You and I are taking very different paths, so my recommendations may not be fully relevant. I’m working on guiding companies how to fix their already broken IT departments while you’re down the technology side. For starters, I’d choose a cloud to focus on, because like it or not, companies use Google, Amazon, Azure or a combination of the three. From there, I’d read probably the most boring thing you can: The well architected framework documentation!
These guides are going to make you ask yourself a ton more questions which will really guide your reading. They will cover most operational topics for that given cloud, but will also apply broadly across all operations platforms.
As mentioned, that Devops handbook is a real barn burner. It tells you what exactly you need to implement to create an environment where the technology, processes and people behind your IT are scalable.
As I said, I’m working on organizational change, and doing so requires that people will agree to work with you. All the technology in the world is worthless if you can’t get people to work with it. So these books were good. I’d recommend reading them simply to help you advance in your career: