It depends on what you're looking for. Books you might enjoy? If so, we need to know more about your tastes. Books we've liked? Books which have influenced us? An overview of the field?

In any case, some I've liked-- Heinlein's Rocketship Galileo which is quite a nice intro to rationality and also has Nazis in abandoned alien tunnels on the Moon, and Egan's Diaspora which is an impressive depiction of people living as computer programs.

Oh, and Vinge's A Fire Upon the Deep which is an effort to sneak up on writing about the Singularity (Vinge invented the idea of the Singularity), and Kirsteen's The Steerswoman (first of a series), which has the idea of a guild of people whose job it is to answer questions-- and if you don't answer one of their questions, you don't get to ask them anything ever again.