For what it's worth, I find that Wikipedia is a great place to learn about more advanced topics in abstract algebra / analysis / category theory. For example,

For what it's worth, I find that Wikipedia is a great place to learn about more advanced topics in abstract algebra / analysis / category theory. For example, the representation theory [1] page gives some pretty good context for how it relates to other fields. It's not the same as a textbook, but generally, after reading the Wikipedia page, I know enough new terminology to intelligently Google for more complete resources like lecture notes, papers, etc.. [1] https://en.wikipedia.org/wiki/Representation_theory https://en.wikipedia.org/wiki/Representation_theory