stingc

They don't exist. At least not if you mean professional physicists or mathematicians. But then you already have a career. There are certainly a lot of interesting things that you can pick up on your own.

A big issue is that problem-solving is really the most important thing in these fields. In what is generally called a Calc 3 class, there are really only a handful of specific types of problems that you're expected to learn about. Once you get the basic idea, that's that. At any higher level, the level of abstraction and "openness" climbs very very quickly. That makes some level of solution feedback much more important. Upper level (beyond freshman or occasionally sophomore year) textbooks also do not have solution manuals or a significant number of examples. They don't repeat themselves like intro books either.

Another thing is that universities generally force you to learn subjects in an order that you might think is boring or unimportant. It can sometimes take an extra couple of years of study to realize that you really did need to know all of that "irrelevant" stuff to fully appreciate and understand the subject. For example you mention studying special relativity a bit. I don't really know your background, but a lot of people try to get into that without a solid background in the physics that came before it. That would be a very bad idea in my opinion. The same follows for any piece of physics, though. It's all connected, and it all builds on what came before.

Finally, when you get into the newer stuff, you eventually come to realize that there are no textbooks you can go to anymore. The vast majority of knowledge in these fields has never been written up for students. There are also disagreements between different authors, and you really need to decide on your own exactly what each conclusion assumes, and how reasonable it is.

Anyway, sorry about being so pessimistic. Good luck in whatever you end up doing. If you need any textbook recommendations, I could probably help you out.