I'm a sci-fi/fantasy fan too. I often find interesting new reading by researching one of the writers I know is good, and finding out the writers that they're friends with or who influenced them or who were influenced by them. For example, I like Alan Moore, who is friends with Michael Moorcock, so I'll give him a go. I like Richard K. Morgan and he was influenced by William Gibson, Poul Anderson and Bob Shaw, so I'll probably give them a go.

It's not the only way to do it, but it's one way. I would never have known about Richard K Morgan if a friend of mine hadn't been looking through a brick and mortar library one day, literally judging books by their covers, found one of his books and subsequently recommended it to me. But once I've found a good writer via whatever means, I usually find that you can follow threads from them to other good writers.