This is kind of like “I’d like to read about the theory of driving a car.” There might be a book on it, but I don’t know of one. It might make you a bit better of a driver, but if you’re trading off time behind the wheel for reading about driving it’ll make you a worse driver. There’s basics and in-depth details that are covered by the docs for any common service you’ll run, and from there you gotta get behind the wheel, have a clear goal, start small, get advice from a community that’s familiar with the services you’re running, and be as risk-averse as you can.
I’m not a professional sysadmin, I’ve only done it as part of jobs when we ran our own boxes, for lab setup for dealing with that hell, and for fun. There are best practices, and important considerations, which the docs for services will cover and you’ll pick up if you’re doing it, but they aren’t grounded in a theoretical framework, AFAICT, and there are no universal axioms that apply to each component that are worth taking the time to learn. There are too many ways to do too many things for a universal theory to apply well. You could study computer science, theories of computation, understand the hardware architecture, learn operating systems in depth, and be better grounded in principles, and that can help for depth, but it’s not that important to most tasks unless you’re doing something really cutting edge or esoteric, and it’s a life-long slog. If you want a high-level work that gives you a nice theoretical framework of the big picture from logic gates down to the OS, Petzold’s “Code: The Hidden Language of Computer Hardware and Software” is good (and fun), but reading it won’t make you any better as a sysadmin.