Hyperion is a good book, as is the 2nd in the series The Fall of Hyperion. However, the two last books are really quite bad. Personally, i found Ilium+Olympos to be his best work.
I found the Culture novels disappointing. Except for Consider Phlebas and maybe Excession, you quickly realize that they are pretty much gods and that there's absolutely 100% no risk...it makes it all quite dull/pointless.
I hated Stranger in a Strange land..maybe I should re-read it. All I remember (and it's been about 10 years)..was that I liked the start, an then it turned really weird...all about drugs and sex and cults.