It's the story of a twin who is called back home after her sister dies in a fire. But dead-twin has been known to mess with alive-twin in the past and appears to be doing so with emails and a scavenger hunt left behind. Is dead-twin really dead? Was it suicide? Murder? Ultimately, dead-twin didn't become a sympathetic character for me until long after I quit caring about her. And alive-twin (and the rest of the family) were so screwed up and selfish that I didn't care about them either. I wasn't surprised by the ending, but I wouldn't have been surprised by other endings either. Overall, the book got so tied up in the whole conceit of the A-Z puzzle that it lost its heart.