Y/A (I think) I read this book whenever I was about 13, and it was about this boy who creates a blog about girls and sex and I think it was based off of his friends diary. The cover was purple and very plain.

[Kaitlyn]

The friend figures out that the main character has written the blog off of her stuff and demands that he stops, and he doesn't so she beats the main character up in front of a restaurant or something.

[Jamie]

Perhaps What Boys Really Want by Pete Hautman?

[Rainbowheart]

Still out there, Kaitlyn?