The probably won't be relevant to most people here, but one book that changed how I approach my work (as a physician) was "Sapira's Art & Science of Bedside Diagnosis". It goes beyond the basics of physical diagnosis and delves into the history and statistics of various physical diagnostic techniques. It even describes a few low-tech techniques and skills which have been forgotten in the US medical system because of high-tech (and more expensive) imaging or lab testing regimens.

Incidentally, I found this book referenced in this article: "Why Should Doctors Read Medical Books?" by Dr. Eric Cassell [0]

[0] http://www.ericcassell.com/download/WhyShouldDoctorsReadMedi...