Fantasy:
Have you read LotR? Otherwise do that. If you have read them, have you read the Simarilion?
I actualy reacomend the Inheritance Cycle, (the first book Eragon might be more well known) I know it has quite a few bad revievs, and it DOES "borrow" a lot of concepts and mechanics from other series but the writing and characrerization is great. I think maybe peaple are just looking at it the wrong way; unlike most fantasy work it does not invent new and unseen things, and prospect ideas for how magic and so might work if it was real. Instead, it picks and choses the best peices from different wors, polish them and fit them togeter, extrapolate and fill in holes. It is nor revolutionary, because it dosn't try to be, it's EVOLUTION, it keeps to what peaple alredy expect of fantasy, and focus on the details, and the normal workings within that framework. The books are not abaut magic, or dragons, they are about politics and drama. Actualy, sort of like DF, the setting itself is generic, what is different is the detail that it is show in, and the intrigue that take place there. [/rant]
David Eddings.
Science Fiction:
It you liked Pratchet, you'll like The Hitch-hikers Guide to the Galaxy.
Is you are looking for classical scifi, maybe something by Asimov?
If you are looking for something more modern, a suggestion is something by David Brin.