LLM's are useful because they can recommend several famous/well-known books (or even chapters of books) that are relevant to a particular topic. Then you can also use the LLM to illuminate the inevitable points of confusion and shortcomings in those books while you're reading and synthesizing them.

Pre-LLM, even finding the ~5 textbooks with ~3 chapters each that decently covered the material I want was itself a nontrivial problem. Now that problem is greatly eased.