Bearing in mind that you're asking this on LessWrong, these come to mind:

Greg Egan. Everything he's written, but start with his short story collections, "Axiomatic" and "Luminous". Uploading, strong materialism, quantum mechanics, immortality through technology, and the implications of these for the concept of personal identity. Some of his short stories are online.

Charles Stross. Most of his writing is set in a near-future, near-Singularity world.

On related themes are "The Metamorphosis of Prime Intellect", and John C. Wright's Golden Age trilogy.

There are many more SF novels I think everyone should read, but that would be digressing into my personal tastes.

Some people here have recommended M. Scott Bakker's trilogy that begins with "The Darkness That Comes Before", as presenting a picture of a superhuman rationalist, although having ploughed through the first book I'm not all that moved to follow up with the rest. I found the world-building rather derivative, and the rationalist doesn't play an active role. Can anyone sell me on reading volume 2?