Rapunzel (hi, welcome back) said that Dune by Frank Herbert is (my favorite SF book).
It used to be my favourite when I was in my early twenties (come back Time, all is forgiven, we found the money on the mantelpiece). I found Children of Dune and the subsequent books less interesting - I felt FH had rather lost his way. However, I found the new novel by Frank Herbert's son Brian and Kevin J. Anderson, House Atreides, to be surprisingly good and every bit as well-written as FH's great first and second books. It's the pre-Dune history of some of the Great Houses and how Duke Leto came to leave Caladan for Arrakis. I see that a second prior history book, House Harkonnen, is out, but I'll wait until the normal-format paperback hits the shelves for that. I expect it to be good, too.
However, the real point to this post was if you like imaginative alternative or future reality books such as Dune which wander down labyrinthine and unexpected paths and byways, then you may want to have a look at the Night's Dawn trilogy by Peter F. Hamilton. Like Herbert, he's written quite a lot of fairly mediocre stuff, but this trilogy, beginning with The Reality Dysfunction, is exceptional.
