As a very inexperienced manager (i.e. startup founder) I found some of the stuff quite helpful, which is doubtless obvious to the more experienced (although, in fairness, I also stopped reading about 3/4 of the way through, but my cofounder swears by it).
(1) Andrew Grove's "High Output Management", it's easy to read: https://www.amazon.co.uk/High-Output-Management-Andrew-Grove... (2) Manager Tools "Basics" podcasts, especially on 1x1s and feedback: https://www.manager-tools.com/manager-tools-basics
There's a hell of a lot to learn outside of these things, but I think they're a good start.