I thought of a few others that are "fun": - The Annotated Turing by Charles Petzold - Quantum Computing since Democritus by Scott Aaronson - Euclidean and No

I thought of a few others that are "fun": - The Annotated Turing by Charles Petzold - Quantum Computing since Democritus by Scott Aaronson - Euclidean and Non-Euclidean Geometries by Marvin Jay Greenberg (a textbook, but an easy one to read on your own) - Gödel's Proof by Nagel and Newman (best if he can read it with a partner and talk through the steps) - Prime Obsession by John Derbyshire Some of those have already been mentioned, but consider this another vote for them. :-)