In our house, Percy Jackson series was the big breakthrough for DS and reading. He also loved the Mysterious Benedict Society books and recently read the three Name of This Book is Secret books. He's currently enjoying a couple of silly little books we picked up today: Flawed Dogs and Zoobreak. I don't claim any literary benefit other than fun - he loves Flawed Dogs (short - about 200 pages; unfortunately, he'll be done with it soon).