[a_c]

Before answering, can you share what do you want to get out from your career? Some starter questions: Why do you want to get into software management? Do you want to get into software management in general, or for the particular company you working for? Is it a stepping stone to your goal, e.g. building your own product?

The books shared in other comments are all good, I personally vouch for the Mythical Man Month. I consider High Output Management a must read for management in general. The Elegant Puzzle is quite useful for team of certain scale, but I would say less useful for startup of a few engineers. Still useful, just less.