Something narrative, I guess. Thanks!
Antony Beevor's "Stalingrad" is considered by many to be the definitive book on the battle. Not only discussing the battle itself, but also the buildup to the battle and its effect on the German campaign.
Depends what you want. If you are looking for a solid, single volume text geared towards the layman, Antony Beevor's Stalingrad is a pretty solid place for you to start. He is an engaging writer who can put together a solid book that makes you want to keep reading. He isn't a guy doing much in the way of original research though.
If you are looking for something more involved. David M. Glantz has a trilogy on the battle, the last book of which only came out this summer, and is considered one of the preeminent scholars of the Eastern Front in World War II, so that is kind of the gold standard.