When I became a new supervisor in 2008, I realized right away that I was woefully under-prepared. My agency offered no training at all! I was a newly minted public librarian so I dug into our collection and started reading. I spent the next decade reading every kind of management book, psychology book, and motivational book I could find.
Here are my reading recommendations for your path to being a better boss:
Read the Ask A Manager blog every day.
If you do nothing else, do yourself a favor and make this regular reading. I’ve been a loyal reader for at least a decade and her advice is consistently the best out there. You can use it as a manager and an employee. The letters she posts are interesting and relevant and often entertaining. The comment section is a great community resource as well.
Thanks for the Feedback by Douglas Stone and Sheila Heen
As a manager you need to give feedback to your staff. But what does that mean? Appreciation? Coaching? Critique? You mean one thing and your employee means another. Clarify your thinking and your message.
Crucial Conversations by Kerry Patterson 
The most critical skill a manager needs is the willingness and ability to have an uncomfortable conversation. Avoiding a hard topic because YOU are uncomfortable is just not an option for an ethical manager. This book is the best place to learn exactly how to do it. Buy a copy for every manager you know.
Nine Lies About Work by Marcus Buckingham and Ashley Goodall
I like my management books to be based on some data, not just feel good inspiration. Marcus Buckingham is that guy. He actually does research to see what works and what doesn’t.
No Asshole Rule by Robert Sutton
This author has lots of other books you should read but this one put him on the map. Why? Because we’ve all suffered at the hands of jerk coworker that management tolerated. It’s never worth it. Don’t be that boss. Create a civilized culture in your office.