I'd recommend Look To Windward, but it wasn't my favorite Banks' book so far. (That's probably Inversions). It took a while to get going, and there were a few too many jumps in time/perspective which I thought detracted a bit from the momentum of the narrative. However, once the reader (finally) figures out what's at stake, it's a tense, unpredictable, and thoughtful (almost philosophical) book set in a complex and interesting milieu (the Culture universe.) Oh, and a great epilogue!