Malazan book of the fallen (12 books series) Absolutely f'kin epic reading. The Gap Cycle and Chronicles of Thomas Covenant by Stephen R. Donaldson are also really good reads. The Gap is a 6 book series about scifi-space-alien stuff, but done incredibly well. Thomas books... hard to explain. They are a bit masochistic to read - and can be incredibly depressive at some junctions (and incredibly frustrating)... but I find myself continuously thinking about what happened in the books and ... well, it just stays with you.
As has been previously mentioned, but I shall back up: Tad Williams: Memory, Sorrow and Thorn Robin Hobb: The Farseer Trilogy They are a couple of my favourite series of books and I've read them both more than once.