I'm interested in the same question. There isn't a definitive text because the problem is infinitely broad. My approach is to build crud apps around the tech stack I'm interested in, currently Python with fastapi, arangodb, with some next and typescript for the front end. But you could swap out Python for Go and swagger. For security there is Keycloak. For scalability you could look at building your system as pods in open shift but that adds cost. Personally, I think unless you're Netflix kubernetes is probably overkill. But the biggest problem is that today's tech stack is replaced tomorrow by the next new shiny, and all of them are complex and will be entirely different for every team and every problem. A book for dev ops is almost impossible.

Back end development is just communicating with a database via http. Rest is experience. I'd recommend trying out something like dotnet where you setup a template and tinker with it and test via postman or something. Then try to use small amount of js to communicate with the server. After that you more or less learned all there is for basic backend and the rest is just pure programming experience and task specific solutions.