Six Months Later by Natalie D. Richards

Chloe fell asleep in study hall.  She does this sometimes (yes, she should be doing her schoolwork, but a quick nap never hurt anybody).  Next thing she knows, she wakes up and it's dark outside.  No one is in her classroom, not even her teacher.  In fact, the building is silent and dark.  Where is everyone?  Then school bad boy Adam shows up and says that she called him.  She can't imagine that.  Why would she have done that?  Why is there snow on the ground? 

Other weird things are happening too.  She has turned into a brain- big time!  She may become valedictorian.  Her grades are excellent and good colleges are recruiting her.  She has always liked Blake- he's cute, nice and an athlete and now he's her boyfriend!!

Of course, there are lots of bad changes too.  Her best friend Maggie isn't speaking to her. They've been inseparable forever. Chloe tried to explain the loss of memory to her parents but they think she is a headcase and take her to see a psychologist.  Chloe has been a little defiant in the past so the changes in her are thrilling them.  Six months have gone by and she doesn't remember a thing.

This book is excellent!  A good mystery with plenty of twists.  Chloe, Maggie, Blake and Adam are all strong characters that I really cared about- I wanted Maggie to tell Chloe what happened to their friendship.  And what's up with the "study" group?  Something is strange about it too.  Who can Chloe trust?