I generally judge a book as good or not good by how many times I put it down whilst reading. This isn't a 100% accurate method, but it's a good rule of thumb. (I have to put down Charlie Stross books for breaks because my brain might hemorrhage otherwise, but his books are still good.) Oh, and tinkle breaks don't count.
So, a really awesome book has none to one break. A better than average book has five or less put downs. Average books get put down by me about ten or fifteen times. Worse than average books...well, I don't always finish those.
Anyway, I had to put this book down thrice. Once was for bedtime. Once was for pizza. And, the final time was to drive my kids to a kid party. I grumbled all three times that I had to put the book down, and really, all of those break reasons are decent reasons. So, I rate this book as an above-average read.
It's a YA books, so the main characters are kids and sometimes do stupid things. Kids not talking about their feelings because they're afraid of what the other kids think seems totally plausible to me. The characters were developed and seemed plausible. Except for dying for 11 minutes, I was a lot like her female character as a kid. (I was a valedictorian, concerned about my grades and the like.) Her inner monologue seemed reasonable to me. She didn't have the answers at once and had to find them, and she wasn't sure of her own feelings. After reading the author's blurb on Amazon, I kind of expected a little bit of science fiction. I mean, she's a science teacher. But it wasn't. And this story was perfect in its non-science-fiction-ness. I kind of wish the complete brain change was explained more, but I'm also glad that it wasn't. Potential discussion topics with the kids: What makes us human? What makes humans different than other critters? Is the differences between humans and other critters important? Is it morally acceptable to help moribund people along their final journey? What does it really take to be happy?