I am currently reading James Potter and the Hall of Elder's Crossing by G. Norman Lippert. It's a sequel (obviously not written by J.K.!) to the series that takes place one year before the epilogue in The Deathly Hallows. It follows James Potter, Harry's oldest son, as he spends his first year at Hogwarts. It's pretty good actually, it definitely has a Potterish feel to it! It's an e-book though, so I've been reading it rather slowly.