[bennyg]

Unbridled curiosity. I highly recommend the book "Surely You're Joking, Mr. Feynman" - it's very good and insightful into how he approaches situations and how his thinking style shapes him and eventually his surroundings.

[thirsteh]

That and "What Do You Care What Other People Think?': Further Adventures of a Curious Character." Some of the best books I've read.

[hkmurakami]

It should be noted that "What Do You Care ..." is comparatively more serious than "Sure You're Joking ...". Two of the longest sections involve the death of his wife during Feynman's days at Los Alamos, and the investigation of the Challenger crash.