Originally Posted by myMind
The Dune Series is one of the greatest acheivments in the history of SciFi literature. I can't recommend it highly enough.
If you want fantasy though try either The Malazan Book of the Fallen series by Steven Erikson or The Prince of Nothing series by R Scott Bakker. Both are excellent.
The Book of the Fallen are good, but be prepared for a whole host of characters that fall in and out of the 11 books. It is difficult at times to keep all them straight when there are minor characters in one book, that become major players in another then completely disappear for the rest of the series.