I haven't read any of his other solo stuff (I probably should) but read a couple of collaborations as well. The Manifold trilogy ('Time', 'Space' and 'Origin') are brilliant books imo, real big concept stuff, lots of science but none of it there to mask a lack of ideas. 'Phase Space', the short...
You should try reading 'Origin' by Stephen Baxter instead :thumbsup:
(edit: in fact the entire Manifold series plus the 'Phase Space' short story collection - proper hard science fiction with imagination :thumbsup:)