I am, admittedly, something of a diehard Sarah Rees Brennan fan. I adored her Demon trilogy, and have devoured several of her excellent short stories. While this probably makes me predisposed to enjoy this book, there's also always the risk that a favorite author will let you down, your high expectations only making the disappointment more acute.My expectations were certainly met here. SRB's distinct and hilarious voice was present in abundance, and there were definitely many giggle-worthy quotes throughout the text. I adore the voice, but I also occasionally thought it was a bit too much--not every character should speak with Sarah Rees Brennan-brand humor, and way too many characters seemed to have the exact same type of snark. With Kami and Jared, who have lived inside one another's heads their whole lives, this is understandable, but Kami's best friend Angela, Angela's brother Rusty, and Kami's dad didn't all need to be on the exact same humor wavelength.Humor pros and cons aside, the book also takes on some more serious issues of identity and selfhood. Kami and Jared are incredibly dependent on one another in the beginning of the book when they think of each other as imaginary, and when they discover each other's existence, a lot of tensions arise. Kami begins to question things like whether she and Jared would get along if they hadn't been forced into one another's brains. Does Jared like Kami because she's Kami, or because he likes the mental connection they share? Would Kami be the same person without Jared inside her head all the time? What would privacy even feel like?All this humor and self-searching is set against a backdrop of mystery as a killer stalks the tiny town of Sorry-in-the-Vale, a killer who may or may not be supernatural in nature, may or may not be related to the recently returned ancient and snooty Lynburn family (of whom Jared is a member), and who may or may not be after Kami herself.I found the ending of this one pretty frustrating--it's one of those not-really-an-ending endings that make you feel like you've just read half of a book and now aren't allowed to read the second half for a year or two while the author writes it. I've read worse instances of this (*cough* Kelley Armstrong's YA books *cough*), but if you're someone who's easily frustrated by that sort of thing, you may want to wait to read this until the trilogy is complete.Overall, despite minor misgivings, this is an excellent start to Sarah Rees Brennan's second series, a YA gothic stuffed full of humor and lovable characters.