One: I'm really grateful to Seanan McGuire for the included Content Warning at the beginning, that let me know while there WAS abusive elements in the early parts of the story, I would not see / be subjected to the worst of it. Gonna send her a message about that as soon as I can get it concise.
Two: While this DOES include gaslighting (and implications of coming sexual abuse) the book is about Abuse as a whole (just in another Portal Fantasy Setting). So Keep that in mind while reading.
Antsy (full name: Antoinette) loses her father early in the story. And gets a step father she has never liked or trusted. When her mother asks for permission to marry him, Antsy refuses, but it becomes clear her Mother just believes it's childish complaints.
And then, the reasons to feel icky around the man continue, starting with Gaslighting to make Antsy look like an untrustworthy liar: after all, why would an adult lie about a conversation or two with children?
He always calls her Antoinette, never Antsy. And of course, the night Antsy Runs (thank god) he starts making more... overt moves on her, and while she does not have the vocabulary for what's happening (and is pretty sure her mother won't believe her even if she found it) she knows (correctly) that she's in danger and runs away.
Anyway, she gets to a thrift store door as nexus. Basically, the premise is: it's where lost things end up (including a lot of money) and when you open a door, you can end up in all sorts of worlds, and do trade.
Here's the catch: Antsy ages (at least) 2 days for every door she opens, and none of the others at the thrift shop TELL her this. They Encourage her to open doors.
So in the span of two years, Antsy (actually 7, pretending to be 9) goes through puberty, and is at a minimum in her late teens by the end of the book. In. Two. Years. So she CANNOT return to her home anymore, realizing the problem.
She leaves the thrift shop (and goes to her home world, where she finds out (I think as a result of her running away) that her abuser is in prison for the Child Pornography the police found on his computer) but wants to eventually return to the thrift shop nexus, because she wants other children who end up at the nexus to make informed decisions about their time, even if they choose to go hog wild with doors.
Basically, the way I interpret it, along with the way her Abuser calls her Antoinette in an attempt to age her into a name that doesn't fit you, is that the book (while being a portal fantasy) is an allegory for the way Child Abuse forces children to grow up too fast. She effectively would have had her childhood taken from the Abuser if she HADN'T gone to the door, and because the runners of the thrift shop were exploiting her, she STILL lost her childhood.
I nearly wanted to cry when I finished the book. It's definitely dark, but it's beautiful. A+ good book would read again