OVERGROWTH by Mira Grant – Review

I received this book for free from the Publisher in exchange for an honest review. This does not affect my opinion of the book or the content of my review.

Overgrowth by Mira Grant
Published by Tor Nightfire on May 6 2025
Genres: Adult, Horror, Science fiction
Pages: 480
Format: eARC
Source: Publisher
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The nitty-gritty: A weird, thought-provoking alien invasion story, Overgrowth won me over with its ideas but suffered from inconsistent pacing.

I have a lot of mixed feelings about Overgrowth, which I’ll attempt to explain below. Overall, this was one of the most unique alien invasion stories I’ve read in quite some time. Mira Grant, who is Seanan McGuire in disguise (in case you didn’t know) has quite the imagination, and I loved a lot of her ideas. However, I do think the execution suffered in some ways, and I’ll admit I have some issues with Grant/McGuire’s dialog across all the books of hers I’ve read, so those issues come into play with my overall thoughts of the book.

The story takes place in 2031 and revolves around a woman named Stasia Miller who, as a three year old child, went missing for three days in the woods near her house. When she finally reemerged, she told everyone she was an alien and her people were coming to invade Earth. Of course no one believed her, because she still looked like Stasia. What her parents don’t know, and what the reader does, is that while in the woods, the real Stasia was devoured by an alien plant and what came out of the woods was indeed an alien.

Stasia is compelled to tell everyone she meets “I am the vanguard of an invading species of intelligent alien plants,” but you can guess how well that goes over. Until one day, an astronomer intercepts an extraterrestrial message from space: the aliens are on the way, and the invasion is imminent.

What follows is a tense countdown to the invasion as Stasia, her roommates and her boyfriend Graham attempt to make sense of what’s coming.

There’s a lot of good in this book, so I’ll start with the positives. The story starts out with a bang, as the prologue describes how everything starts: an alien seed pod flies through space and lands in a forest in Washington state, where it takes root and grows into an unusual flower. This idea of alien life sprouting from plants is so cool, and as you get further into the story, even more interesting details about this invasion are introduced. The opening scene when little Stasia is killed by one of these plants was horrifying, and it set the tone for what’s to come. I also liked the author’s nods to stories like Little Shop of Horrors and The Day of the Triffids, and Stasia even names her cat Seymour.

Grant often infuses her stories with issues that are important to her, and in Overgrowth she tackles some big ideas, like what it means to be human, how we fit into the universe, and do humans have enough “good” in them to be considered non threatening to an alien race. Colonialism is a big theme in the story as well. The aliens are the invaders who plan to colonize Earth, but there are also some sections where government agencies find out about Stasia and arrest her in order to perform experiments on her. It was never clear who was “good” and who was “bad,” which is one reason these themes worked so well. Stasia herself seems to be conflicted over the answers to these questions, even though she isn’t technically human and is in fact part of the coming invasion.

Which brings me to Stasia’s character, who I liked a lot. Stasia doesn’t really like humans, and she’s what we would call an introvert. But over the years she’s managed to find some humans who become very important to her—her boyfriend Graham and her roommates Lucas and Mandy—and here’s where the conflict comes in. Of course, she doesn’t want anything bad to happen to them when the aliens arrive, but as she becomes more alien and starts to develop certain, let’s say appetites, her alien nature starts to take over. I loved the way the author handled this change in her personality, and it solidified the fact that yes, this is a story about bloodthirsty aliens, despite some of the more feel-good, found family moments. 

Grant also includes a trans-man character (Graham) and describes what seems to be a very healthy and normal relationship between two adults. Graham and Stasia have gone through many ups and downs during their relationship, and despite the downs they are deeply in love and have managed to stay together for years. A few other characters were standouts for me, especially Toni, the scientist who intercepts the alien transmission, a woman who was also attacked by an alien flower as a child (just like Stasia) but managed to get away (and she has the physical and mental scars to prove it), and Jeff, another alien who Stasia meets and bonds with during the invasion.

Now for a few issues I had, starting with the pacing. After an exciting opening, the middle section of the book stalls and becomes repetitive in places, only to rev up the pace in the last 20% or so. Overgrowth has a fairly large page count, almost 500 pages, and for me it was just too long. Some sections could have been cut entirely and others trimmed. Grant has a lot to say, especially about the emotional state of her characters, and often the action screeches to a halt so everyone can discuss their feelings in detail.

I also had a hard time believing that Stasia, Graham and her roommates were in their mid-thirties. Their dialog comes across as almost YA in tone, and sometimes the issues and themes the author is addressing interfere with natural dialog, as if the characters decided to step up on their soapbox and lecture the reader. I wanted the themes to be more integrated into the story, but instead the dialog often came across as forced.

And without giving too much away, I will mention there are some very goofy things that happen in the last section that didn’t work for me at all. It was almost as if creepy alien plants with killer tentacles weren’t enough, so Grant decided to add in a few additional and completely out of place creatures to cause even more havoc. 

Stasia, who is telling the story, telegraphs quite a bit throughout, saying things like “it was never going to end well” or “we warned you,” leading the reader to believe that the coming invasion is not going to be a peaceful one. I found the ending rather depressing overall, especially since there was a twist late in the story suggesting that humanity could be saved, if only someone had done this one particular thing.

But complaints aside, Grant has written a complex, thoughtful and chilling alien invasion story that gives readers a lot to think about. Despite my quibbles, I’m very glad I read Overgrowth.

Big thanks to the publisher for providing a review copy.