I discovered the fountainhead last year and I found it fascinating although it becomes more and more awkward as you progress. At the end it seemed to me like a journey into a sick mind, which makes it all the more interesting.

I would recommend semi-autobiographic books by sick minds.

Zen and the art of motorcycle maintenance, by Robert Pirsig who was actually treated by electrotherapy in a psychiatric ward. He ended up writing a not so sick book with a philosophy I find a lot more convincing than Ayn Rand's.

Valis, the novel in which Philipp K. Dick describes how he more or less fails to make sense of his religious (or whatever) experience. It's sold as science fiction, but that's just a weak way of saying that book is completely crazy. Since it is semi-autobiographic, the characters are much more alive than in anything else I read from Philipp K. Dick.

And if you want to know why Howard Roark has a low life expectancy:

Loneliness, human nature and the need for social connection, by John T Cacioppo and William Patrick. This is non-fiction.

Lolita by Vladimir Nabokov

The Great Gatsby by F. Scott Fitzgerald

One Flew Over The Cuckoo's Nest by Ken Kesey

Nonfiction:

Market Wizards: Interviews with Top Traders by Jack D. Schwager (1993)

Guns, Germs, and Steel by Jared Diamond (history)

If you enjoy history you may want to read Michael Shaara's The Killer Angels (historical fiction). I loved it.

if you liked the Fountain Head you can read The Selfish Gene by Richard Dawkins ( insight into evolution ) - http://en.wikipedia.org/wiki/The_Selfish_Gene

I am going to get through Warren Buffett's biography, The Snowball.

The Da Vinci Code (haha remember when that was huge)

Anything by Terry Pratchett.

Non-fiction but a great read:

Surely You're Joking, Mr. Feynman! by Richard Feynman

http://en.wikipedia.org/wiki/Surely_You%27re_Joking,_Mr._Fey...!