Books on Transhumanism
What Technology Wants by Kevin Kelly, introduces the concept of technology as the 7th kingdom of life, growing and evolving just as all living things do. Great book for framing a lot of transhumanist discussion in a connected and comprehensive way. The Inevitable is Kevin Kelly's most recent book, focusing on more specific ways technology will change over time.
Ending Aging by Aubrey De Grey. I haven't read this book specifically, but de Grey's thought and research is what I engage with in the discussion of radical life extension.
The Singularity is Near by Ray Kurzweil. Kurzweil argues that we're about to experience a 'Singularity', an intelligence explosion, where the intelligence embedded in our technology becomes greater than the intelligence embedded in human brains. This book explores what kinds of ramifications that might have for our near future. Ray Kurzweil is a long-time inventor, and has recently been brought onboard at Google to work on constructing an AI.
Engines of Creation by Eric Drexler is the seminal work on nanotechnology, and everything it is capable of. Eric has written a more recent take on the subject here.
The Beginning of Infinity by David Deutsch. The inventor of quantum computing explores the systems in physics that have infinite reach—including the human mind. Not specifically transhuman, but great physics-as-philosophy, and will change your perception of what we're capable of.
Human Purpose & Transhuman Potential by Ted Chu, examines the philosophy of human purpose, and shows how humanity coherently understands itself as the self-transcendent species.
The Transhumanist Reader, for completeness. A newer compilation of essays, which I haven't yet read.