Dan Simmons Hyperion Series
including Endymion and the 4th book.
Simmons is the best WRITER to have ever graced SF. Period.
The Hyperion stuff combines a fully fleshed out future history... space opera...conflict between humanity and AIs...religion...horror...adventure...a non-yucky love story..and really richly textured speculation on good vs evil and the conflict echoing throughout time from the end of time backwards.
My 2nd favorite series would be the Galactic Center theme novels by Greg Benford, a fine writer.