Slightly more grown up than Pinkilicous, is Devilish by Maureen Johnson about a cupcake munching demon intent on gaining the schools of high school girls in exchange for popularity and good hair!
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, cupcake nibbling demon...without losing her own soul in the process.
I bought this a few weeks ago after being recommended it by Amazon, and while its obviously meant for teens it was quite an enjoyable read!