Oh god, this concept is really scary.
Check out this website:
Here.
Basically, if you're a teen girl between the ages of 12 and 13, you beg your parents to buy one of these books for you, and you are then written into a Twilight-esque, poorly written teen romance as the main Mary Sue character.
What could be more fun? (Sarcasm)
It actually seems like a pretty good money making idea, if you're willing to sell your soul to the literary devil.