One of the non profit groups I volunteer for is assembling a recommended reading list for postdocs, and I contributed a few titles. These are all applicable to a broader range of scientists than postdocs.
Making the Right Moves, available for free. Information, what to expect, and advice for early career investigators from grad student through junior faculty level.
Advice for New Faculty Members by Richard Boice. I recommend this for postdocs whether they are considering a faculty position or other. It has great advice on writing and on career socializing, and on teaching for those who might be doing that.
Intuition by Allegra Goodman. This is a novel about research misconduct. It would be a good discussion point for an RCR class. It is entertaining and thought provoking, and reading it will help you understand the consequences of some difficult decisions you will face, such as dating someone in your lab or what to do with your suspicion of someone’s misconduct.
Moo by Jane Smiley. This is a novel about Moo University, a fictional midwest university that seems eerily familiar to anyone in any midwest university! It’s a great stress relief, but also educational in understanding the vagaries of politics in academia.
PHD Comics (the books or the web comic). While PHD Comics started with grad students, postdocs make several appearances and Mike Slackernerny’s recent transition to a postdoc position puts postdocs on the stage. Whether you are a grad student or a postdoc, PHD Comics provides a humorous perspective but also enlightens us that the frustrating quirks of our PIs are uncomfortably common.