Sherwin Nuland lists top 5 books that were Turning Points in medicine in this weekend's Wall Street Journal:

1. Interpretation of Dreams by Freud
2. The Double Helix by James Watson
3. The Silent World of Doctor and Patient by Jay Katz
4. Microbe Hunters by Paul de Kruif
5. The Merck Manual of Medical Information: Home Edition

To that list I would add On Doctoring, an anthology of writings about the art of medicine commonly given out to US medical students at the beginning of their training.

H/t Med Pundit