Chukkypig - if you like sci fi that deals with questions about mutable identity etc. then you might enjoy C J Cherryh's Merchanter Universe novels. There's several and you can read them in order or not, although I'd probably start with Downbelow Station just because it's the first and sets you up well to understand the reality she's created.
A lot of people don't get on with her stuff because she can be quite unforgiving in terms of not spoonfeeding the reader information about the created reality - she just sets it up and assumes you'll understand it. But her characters and ideas are so brilliantly formed and expressed, it's worth it IMO. Cyteen is one of my favourite books ever (as my username probably makes clear). The Merchanter novels deal a lot with cloned humans and the ways in which people's personalities are shaped, artificially or otherwise. Downbelow Station is also a fantastic thriller.
She writes excellent fantasy too, again full of fallible, complex characters who make mistakes and don't spring straight back from a beating. The Chronicles of Morgaine is a great book, weaving some interesting sci fi ideas among the crunchy sword'n'horse action.
Otherwise my top fantasy recommendation is the same as always: George R R Martin, the Ice & Fire books. Massive, finely drawn, grimly amusing, realistic, often horrifying, always fascinating. The first three in the series are three of the most satisfying books I've ever read.
Recently finished China Mieville's Perdido Street Station and enjoyed it, once I realised I was reading a ripping yarn rather than a more subtle Mervyn Peake style introspective. His writing tends towards the overcooked - a good editor could easily lose at least 200 pages of repetitive, unnecessary description and the book would be much the better for it - but it's a good romp.