Since the relationship which makes this review relevant to this comm spans the entire trilogy, I will be talking about all three books here, rather than singling one out. I will try not to drop detailed spoilers, but some later-game reveals might be necessary for context. Please read accordingly.
Millie's life has gone spectacularly to shit about a year ago, following a suicide attempt which left her with two prosthetic legs, brain damage, and metal pins all through her body. She expects to stay in a mental institution until her money runs out, when she's approached by Caryl Vallo, with an invitation to join the Arcadia Project, a secret organization which often hires mentally ill people as liaisons to the Seelie and Unseelie Courts of faerie. Though Millie's not optimistic, and her Borderline Personality Disorder means she has a tendency to alienate those around her, she decides to give it a whirl. For her first assignment, she's tasked with finding a missing faerie noble, and the politics of the courts and the Arcadia Project itself only get thornier and more twisty from there. For one thing, the very magic from which fae and humans alike weave spells may be more complicated and sentient than the Powers That Be would like you to believe. For another, every fae has a human that they are linked to, somewhere out there, called their Echo. The two experience a soulmate-like attraction upon meeting (it doesn't have to be romantic or sexual, but it's very intense.) But more importantly, such links fuel human creativity and make up the backbone of major human progress, while grounding the fae, who are normally incapable of forming long-term memories.
And then, there's Caryl, who may appear competent and no-nonsense at first, but who's just as traumatized, impulsive, and fucked up as Millie. The two are drawn to one another, even though they know any sort of relationship would be a terrible idea. And before you ask, no Caryl isn't Millie's Echo, so they don't even have that convenient excuse for their inability to keep their professional distance.
I've read way too many books with lesbian relationships where I've gone, 'this is fine, they're nice people, they deserve a happy ending,' but nothing about the writing actually made me care.
And then there's Millie and Caryl. They are both trainwrecks, and I love them, and I want them to kiss, even if the reasons they really shouldn't are one-hundred percent relevant and important. It helps that they feel like deuteragonists rather than a protag-and-love-interest. Both are vivid and emotional, both have their own scars.
In general, I love Millie in all her prickly, self-destructive glory. Her voice is vibrant, funny, and heartbreaking. The secondary characters are also great, morally gray enough that you can't automatically point at someone and call them a villain or a hero, and even people who do terrible things may have compelling motivations and or personalities. The portrayal of Millie's physical disability and mental illness is top-notch. Neither is sugar-coated, but neither strips Millie of her agency (and boy does she have agency!) The worldbuilding is great. Baker's Los Angeles lives and breathes, and so does her Faerie.
It's worth knowing that A) the books are primarily focused on action and plot, with relationships developing inexorably in the background; B) in addition to Caryl, Millie has another love interest (a guy, whom I also like a lot,) and a fuck buddy (whom I like less, but then so does Millie;) and C) there's no guarantee of a happy ending, all across the board. Nonetheless, the trip is well worth taking. ( Some spoilers on the ending )