Overgrowth by Mira Grant Review

Day of the Triffids meets Little Shop of Horrors in this smart, charming, harrowing alien invasion story about being human, by a Hugo-award winning author.
 

Since she was three years old, Anastasia Miller has been telling anyone who would listen that she's an alien disguised as a human being, and that the armada that left her on Earth is coming for her. Since she was three years old, no one has believed her.
 

Now, with an alien signal from the stars being broadcast around the world, humanity is finally starting to realize that it's already been warned, and it may be too late. The invasion is coming, Stasia's biological family is on the way to bring her home, and very few family reunions are willing to cross the gulf of space for just one misplaced child.
 

What happens when you know what's coming, and just refuse to listen?

Most sci-fi alien invasion stories are told from the frontline defenders, innocent bystanders, or the invader themselves, but not many are told from the perspective of the early vanguards planted in place to test the soil before the interstellar fleet arrives (sorry couldn’t resist the pun). Putting a unique botanical spin on the classic alien invasion story, Mira Grant’s Overgrowth is a unique, intellectual, and ambitiously crafted novel written from the perspective of Anastasia Miller who has believed herself to be an alien for nearly thirty years. Constantly telling others she’s an alien sent ahead of an invading armada for years and being written off as an eccentric oddity, her unassuming life in Seattle is upended when an alien signal is received announcing that said alien armada is finally coming to Earth. While most stories of similar content show off the epic scale and flashy combat of the invasion, Overgrowth instead chooses to focus on the ramifications for individuals like Anastasia, with conflicting loyalties and the often cruel and destructive nature of human behavior on full display. Featuring slow pacing interrupted by frequent political and social commentary, Overgrowth is not for everyone (myself included), but it’s nonetheless an intriguing sci-fi story that’s unlike anything I’ve ever read.

Before I get into my thoughts and review of Overgrowth, it’s important to address the frequent confusion about the novel’s genre and narrative content. When Overgrowth started getting early ARC reviews and was announced as a special edition pick for Illumicrate’s Starbright sub and Owlcrate’s Sci-fi subscriptions (this is the version I have), there was a lot of confusion surrounding this book and whether it was a horror novel or a true sci-fi novel. Goodreads lists it as horror before sci-fi and its US publisher Tor Nightfire (Tor’s horror imprint) features editorial reviews from other horror authors as well as pushing a very dark, twisted marketing approach. While humanity’s outlook is grim and there are certain elements of the invading aliens that have unsettling aspects, most of the book’s content is most certainly sci-fi. While I understand that Overgrowth‘s sci-fi elements are hard to market and sell without giving away major spoilers, I feel it’s a huge disservice to this book as I’ve seen more than a few sci-fi readers actively avoid it, fearing or being disinterested in horror novels. For fans of horror novels, this also sets up the book to disappoint, particularly when the story pivots into its otherworldly hard sci-fi content. The prologue is the most horror-centric chapter both in tone and content and can be quite shocking to sensitive readers (check your trigger warnings ahead of time), but outside of that, I would consider the rest just alien-flavored sci-fi. While I read both sci-fi and horror genres regularly, I generally prefer sci-fi more and was relieved with what I got as I most certainly would not have chosen to read this, let alone buy this novel based on its horror marketing (I’m also blind and thought the trade cover art was a fern enveloping a glowing green eyeball, not the planet Earth).

My gripes with the confusing marketing aside, Overgrowth is an intriguing novel that has a lot of layers and metaphors present everywhere you look. Both at a surface level as well as deeper, subtler connections, Grant’s use of the being “alien” is a recurring theme that has multiple meanings throughout the story. Being an alien is applicable to almost any social group or minority who is the subject to xenophobic prejudice, one example being Anastasia’s roommate Mandy who is Mexican American, a timely and appropriate reference to the trajectory of the current American federal administration. Socially challenged, ostracized, and unable to lie or deny her alien heritage, Anastasia’s eccentricities can also be interpreted as being lightly coded for being on the spectrum. Additionally, those that are alien face the question of where their loyalties lie as well as the age-old discussion of nature vs nurture. For some aliens like Jeff who spent their entire life in isolation, the coming is an open arms embrace and welcome home. Yet for others like Anastasia whose friends have accepted and loved her, the answer is far more nuanced and uncertain. I can see a valid argument being made that this is also a metaphor for the immigrant experience and the internalized conflict of one’s cultural identity, though I may also be reading too deep into things. Regardless, underneath all the alien invasion discourse and sci-fi goodness, there’s some sort of commentary noted at every turn which adds extra weight throughout the story.

Although this novel was published in May 2025 and the finalized manuscript due much earlier, Grant’s political criticisms of the American government and administration is also startlingly prophetic and grim. Once the alien signal is detected, Overgrowth’s version of the American government of 2031 immediately denies aliens in America their citizenship status and rights, rounds them up very similarly to the recent ICE movements, and displays their agents and soldiers going rogue. Those accused of being aliens are also subjected to hate crimes not unlike those towards minority groups both ethnically or socially, and the shared connection via a forest haven Anastasia and other aliens find in each other is quite the metaphor for real-world issues. Without giving away any spoilers, the invading alien force are also fully sentient and have their own ideology on survival, planetary life cycles, and a clear opinion on humanity’s existence. The well-crafted ethos of the aliens, their motivations, and the interesting parallels and differences to humans are well-written and imaginative; Mira Grant/Seanen McGuire is a great writer.

The book is divided into several sections and arcs of the story. Though the trademark sci-fi elements take a backseat for the entire first half of the story, they’re quite compelling and interesting once they come into play. The strategy and purpose for the alien vanguards on Earth, the spread of the botanical forces, the otherworldly visuals along with the peculiar plant/human hybrid biology, Grant’s creative ideas cement Overgrowth as a true sci-fi novel. A healthy balance of plausible pseudo-science that isn’t overly technical to understand nor unexpectedly random, I found the sci-fi content to be great, when the book chooses to stay on-topic that is.

While I thought Overgrowth a fascinating read from a creative and analytical standpoint, I found myself often struggling to stay invested in the story. Part of that has to do with the novel’s very slow pacing and its noticeable lack of action and excitement. While I understand the primary intent of the story is the political commentary and metaphors previously discussed fused with the out-of-place dysmorphia, it’s impossible to overlook and acknowledge how little of the alien invasion is actually experienced and how underwhelming the interstellar contact is, a recurring point highlighted in many reviews for this book. There are occasional moments of action or surprise twists that show strong signs of life, but they’re very brief and understated; at least 90% of Overgrowth is simply characters talking about the alien invasion and its hypothetical effects.

While already low on action, the pacing feels even slower due to the frequent flashbacks to Anastasia’s life in Seattle, childhood, and memories. While they’re not poor by any means, they feel excessive to the point that they feel off-topic and actively hinder the reading experience. Nearly all of the first hundred pages are used to establish how socially rejected and out of place Anastasia is, which gets repetitive quickly after the point is made. While I also appreciate and applaud the intent of Grant’s strong political and social commentary, not all of them feel appropriately placed and utilized, though this improves substantially in the second half of the book. I often went back and forth on my opinion that the plot was too sparse originally and needed to be expanded with this additional material, or that the story was too meandering and needed to be edited down a good 100-150 pages.

What is perhaps a bigger issue is the way the story is set up and plotted. Despite being definitively a sci-fi novel and quite a well-crafted one at that, there’s an extremely limited amount of sci-fi content present until about 60% in the book. Part of that is necessary given the novel’s premise of Anastasia discovering who and what she is over time and learning about the intent of the alien invasion. Even with that in mind however, I feel like more sci-fi elements could’ve been incorporated to add more interest or limiting some of the more extraneous details about her isolated life. Anastasia forest-walking dreams that are the visual inspiration for both Owlcrate and Starbright’s special editions were a good start, but more was still needed. I consider myself a big sci-fi fan and do not mind slow-burn stories or those that are more human-focused compared to the more flashy and techy areas of the genre (Robert Charles Wilson or Arthur C. Clark some to mind), but even I struggled with Overgrowth‘s first half. The first three sections have a distinctive lack of direction other than “the alien invasion is coming!” and the excessive amount of slice-of-life/socially challenged content feels more like a women’s fiction or contemporary drama novel, potentially discouraging hard sci-fi fans from continuing. Yet once the story hits the 60% mark, the novel goes full-on otherworldly sci-fi with its interplanetary scope full of imaginative and alien concepts, resulting in a potentially whiplash experience for non-sci-fi readers not expecting it to come. A quick look at many other reviews for Overgrowth confirms that sentiment with some finding the first half lackluster, boring, or off topic compared to the back half (I fall into this camp). Then you have a huge number of reviews that enjoy the out of place character narrative of the first half, then feel like the story goes off the deep end into a confusing mess of horticulture jargon. To make matters worse, both Grant and Overgrowth‘s general tone and opinion of the American government is fairly cynical and nihilistic (this novel is liberal-leaning and not recommended for conservative valued readers) which is represented by its bleak and inconclusive ending. While I personally found the ending respectable and thought it matched the story’s mood well, it’s not one that a casual or optimistic vibe kind of readers will find satisfying at all.

Another area that I was a bit mixed on was Overgrowth‘s character work. The journey Anastasia’s character goes on and her shifting opinion towards other humans and plant aliens is excellent, particularly her ideological shifts and the conclusion that no living being is perfect or well-meaning.  Her fish-out-of-water experiences and difficulty with others were also well-written and presented, relatable to introverted and unintuitive folks despite the point being excessively hammered home. However, I often felt like the other characters were underdeveloped or unnecessary due to the story focusing on areas I wasn’t personally interested in. Mandy and Toni were easily my favorite and most interesting, particularly Toni’s eccentricities and her unabashed outspoken nature (all the laughs I had while reading were courtesy of Toni being a scene-stealer). However, others like David felt like they were added bloat to the story as well as Tahlia who probably could’ve merged with the Senator’s character narratively. Compared to Mandy, Anastasia’s other roommate and friend Lucas felt like an afterthought and despite them being close, the reader is never given proper context or enough of a backstory to back it up. This is most noticeable when characters are at risk in the invasion, having to choose sides, or are facing moral dilemmas in the face of dire circumstances. There are moments that are clearly meant to be important and dramatic that I felt were just kind of “oh, okay then” due to not caring enough about the characters. It’s not for a lack of effort, as evident by the many flashback tangents present in the first half of the book, but the quality or narrative content in these flashbacks felt lacking in substance. The best parts for me were when the character reminisced about how they first met, college life, and other shared experiences that really show the reader their close friendship is. The excessive amount spent on Lucas’s girlfriend Roxanne felt like wasted time that could’ve been focused more on Lucas himself, given the point made about her dislike of Anastasia could’ve been achieved in a few pages at most.

On-brand for Mira Grant/Seanen McGuire’s books, Overgrowth has a great queer representation most notably via Graham who is a trans man. Running with the alien premise and the recurring theme of Anastasia telling people who she is but being ridiculed and rejected, this is a perfect metaphor for the trans community that is denied their identity both by many in society as well as government entities. The camaraderie shared by others not believing that Anastasia isn’t human while others saying Graham isn’t a man was a really effective and powerful statement that I wasn’t expecting. The conflicted feelings and relationship dynamics between them as Anastasia’s plant and alien experiences progressed was interesting, though I wish more time had been spent introducing them as a romantic couple. As it is Graham came into the story relatively late for how important he is and while Grant had a lot of great flashbacks and content covering his trans identity and commentary on the queer community, I felt there could’ve been more content about him as Anastasia’s boyfriend as well as his character personality in general. I personally wasn’t very interested in their relationship, which robbed most of their critical moments of the tension and impact they should have had. Additionally, because so much of the back half of the story is focused on Anastasia and Graham’s uncertain future, Mandy and Lucas take a backseat in the story despite them being more distinctive compared to Graham (though at least Mandy has some great moments towards the end).

Creative and impressive on paper, I often found myself liking Overgrowth far more conceptually than actually experiencing it. Full of strong commentary and symbolism everywhere (not to mention accurately predicting where the American government would go in 2025), this fusion of sci-fi flavored metaphors connected to a deep humanity-focused story is a solid high-concept premise that should’ve been perfectly up my alley. Unfortunately, the slow pacing, frequent tangents, and disconnected halves of the story left me with a rather conflicted impression of the novel. Though I didn’t enjoy reading it and found it difficult to get through (difficult due to lack of interest, not due to finding its content off-putting like some other reviewers), I nonetheless appreciated how unique and ambitiously crafted it is. While this is not a book I can comfortably recommend to most people due to its presentation and awkwardly imbalanced sci-fi content, it is one that is worth trying out if you’re looking for something intellectual and a bit off the beaten path (definitely a candidate to rent/borrow the book before buying if possible).