Having not managed to finish a Stephenson book since "Snow Crash" (which I liked) i may not be in the best position to recommend something to you, but I really like Greg Egan. Truly idea-driven SF which also has interesting enough characters and story. I also like that his books are pretty short, even his trilogy is probably shorter than any single Stephenson book. Very little "fluff".
_Diaspora_ and _Permutation City_ are both excellent. If you don't want to commit to a full novel, his short story collections are all fantastic as well.
