Wow. This book totally drew me in and would not let me go. I found myself reading it everywhere, completely caught up in the characters and the story. I've never read a mystery that kept me so entertained and interested in where it was going. I bought myself a copy midway through (a brand new copy; I rarely buy new books) because the copy I was reading was on interlibrary loan and coming due. I had to finish it.
Ultimately, even after finishing it, I still love the book even though I reacted pretty emotionally to the ending. Books rarely knock me back and leave me stunned, but this one did. My emotional reaction to the characters' actions (particularly the protagonists') told me that I was really connecting with the book, even in a negative way. I may not have liked the ending, but it was pulled off skillfully.