I'm thinking of a book that you can ask questions. It can explain topics in more detail, or it can tell you that the thing you asked will be explained later in the book. And it will allow you to skip material that you are already familiar with. Provide references to other resources, etc.
Maybe ingesting an entire book is too much for current LLMs, but I'm sure there are ways around that.
Note: I am __not__ trying to build such a tool myself.