Reading The Book of the New Sun atm. It's quite a dense read, and you may find this useful: Lexicon Urthus: A Dictionary for the Urth Cycle. I find myself having to refer to the lexicon every other page, but it's worth it.

If you're looking for a complex fantasy series that will occupy you for a long time, I cannot recommend Malazan Book of the Fallen enough!

Have you read Titanium Noir by Harkaway? Mixture of S.F. and noir. Very engaging, I read most of it in one evening.

Barbed Wire Heart by Tess Sharpe is an excellent thriller.