I'd echo @matty.wtf's suggestions for devrel specific books.
I also think reading developer foundational books for whatever company you are working for is important, since you need to know the lingo and understand the problem space (link.springer.com/book/10.1007... was great for me).
link.springer.com
Solving Identity Management in Modern Applications
Design identity and access management for your applications, including account creation, session and access management, account termination, and more.
