I recently finished Fads and Fallacies in the name of Science Before that, I loved
~The Dead Sea Scrolls Deception
~The curious incident of the dog in the night time
~All of Ayn Rand (but with a gap of 6 months or so, else it becomes monotonus)
~Arthur Conan Doyle
~1000 unsolved mysteries
~Clive Cussler (only the Dirk Pitt series though)
I frequently haunt http://www.gutenberg.org/ Sometimes you discover real gems. I recently came across Gibbon's Decline and Fall of the Roman Empire. Yet to start on it though. I love reading about history. Gives me a feel how the real life and culture and thoughts of a period. Works of Josephus and Pliny are on my to-read list.
I'll stick to contemporary authors, as a lot of the classics are already being mentioned.
I recently read through all of Michael Chabon, and he is awesome; the only thing of his I might not recommend would be "Mysteries of Pittsburgh", his first, before he really found his voice (and even that ain't bad.) The Yiddish Policemen's Union, The Amazing Adventures of Kavalier and Clay, and Wonder Boys all rock.
Connie Willis (To Say Nothing of the Dog,) already mentioned, is generally great, too. Doomsday Book is another wonderful read.
Karen Maitland's "Company of Liars" is a more obscure but surprising choice.
Jonathan Safran Foer's "Everything is Illuminated" and "Extremely Loud and Incredibly Close" are both wonderful.
If you like long stories, and have some disposable income, pick up Steven King's Dark Tower series. 7 books, and I loved all of them. If you are a big SK fan, or have even watched some of his movies based on his books, there are a ton of tie-ins. Others I recommend:
Lord of the Rings (no explination needed)
The Once and Future King (Story of King Arthur from small boy through his death)
Devil in the White City (Story of teh Chicago World's Fair and a real-life serial killer)
Hitchiker's Guide to the Galaxy and its subsequent books (Great humor, great sci-fi, but the last book Mostly Harmless wasn't as good as the rest)
These are just ones off the top of my head....I could check through my collection and see what else is there that would be fun reads.
When I die, I want people to look at me and say "Yeah, he might have been crazy, but that was one zarkin frood that knew where his towel was."