About The Book:
Written by Maureen Johnson Published Year 2006
The only thing that makes St. Teresa's Preparatory School for Girls bearable for Jane is her best friend Ally. But when Ally changes into a whole different person literally overnight the fall of their senior year, Jane's suddenly alone--and very confused.
Turns out, Ally has sold her soul in exchange for popularity--to a devil masquerading as a sophomore at St. Teresa's! Now it's up to Jane to put it all on the line to save her friend from this ponytail-wearing, cupcakenibbling demon . . . without losing her own soul in the process.

Feels like a start of a series, I think it will make a good series, hope Johnson makes a sequel. It was pretty weird err different, I think alot of her novels are somewhat unique but this more than the others.