Bubble, anything by Marian Keyes. The woman is a literary genius. Also I have to recommend the Harry Potter books, I'm on to the last one at the minute and only started reading them at xmas, can't put them down. I know I'm 27 but everyone I know has read at least one of them and has loved it.
Watermelon by Marian Keyes is an amazing book, all of her work is excellent, but this is the best. Shazbang is spot on.
Sophie Kinsella also writes under another name, and has published some really good other books, but for the life of me, I can't remember her pseudonym right now.