Chronicles of Thomas Covenant, but Stephen Donaldson is great, first series is great, second series is first series reprised and i haven't had a look at the third series yet. also his Gap into series is good train fodder.
I liked Terry Brook's Knight of the Word series before he melded it into the Shanarra series, was a good alternative 'fallen knight' scenario.
L. E. Modessit's Cyador series is an interesting read, writes the tale from the perspective from both sides who believe they are the good.
Grunts by mary Gentle is a must, it tells the tale of the 'last battle' from the perspective of the Orcs, absolute pisser, and well written, such classic quotes as 'pass me another elf this one is split'
I love discworld books have read most.
Lord of the Rings, and the Silmarillion are among my favourites.
new favourite is 'American Gods' by Neil Gaimon (look up the books of magic, a graphic novel/comic series from the late 80s featuring a boy wizard with dark hair, a scar on his forehead and a pet owl, who is the next great magician), also wrote coralyne. absolute genius IMO.
the Abhorson series is dark and hard to get into but once in, you are caught, but Garth Nix.
Reimond Feist's series is a lot of fun, and a whole world to contemplate, although he did the dirty on his partner in crime from a spin off series
Fritz Libres Fafhrd and the Grey Mouser is a lot of fun.
the vast collection by Michael Moorcock is both simplistic and complex and can be fun, i loved them.
Philip Pullmans 'his dark materials' starts of well, but tries to capture too much laterly i thought, but still a ripper read.
Julian May's many coloured land and the prequel series is fantastic and I loved it, wish she wrote more but its a closed series now i believe

I too am a fan of asimov and less so clarke.
the Illuminatus trilogy is a great read, especially if you like books that are written by people on speed who take valium to slow down and then hallucinogenics to stretch out again, Robert shea and Robert Wilson.
Larry Niven and Jerry Pournole the Mote in God's eye is a fine two part series.
Anything by David Brinn is worth a read, earth, the postman etc, i love his staff, and writes too slowly for me
