Hmm if you want something fun but not as fluffy as the Shopaholic Series I'd suggest that Jennifer Weiner's books are pretty good. You could do Good in Bed, In Her Shoes & Certain Girls (Just came out today & is the sequel of Good in Bed).
Marian Keyes also has some great books. A bunch of hers-Watermelon, Angels, Is Anybody Out There & Rachel's Holiday all involve the same family (the characters are absolutely hilarious).
Jhumpa Lahiri's books are also amazing. She's the writer of The Namesake, Interpreter of Maladies & Unaccustomed Earth (Came out last week).
Alice Hoffman is also fantastic. I loved Skylight Confessions, Blackbird House & The Probable Future. She has a book called Incantation. It's a YA book, but I think it's one of her most powerful books in terms of themes.
Jonathan Safran Foer is one of my all time favorite writers. He wrote Everything is Illuminated & Extremely Loud and Incredibly Close. Very cool books, slightly funky. To make it a trio, add his wife's book The History of Love. Her style works very well with his.
For classics, there's nothing wrong with reading Jane Austen's books like the book club. Miss Austen's books are my guilty pleasure.
