dumb question, but what is the best way to feed the book to the llm?

i run into context window limits, or practical limitations of digitizing the book

You need a non DRMd copy of the book. You don't have to feed it all at once, although with a 1M context limit it is doable. A few chapters at a time is enough, in my experience. An easy alternative is using NotebookLM (now Gemini Notebook), and that has worked brilliantly for me, but I haven't tested it for technical topics (for that I like the LLM to create graphs and e.g. interact with Mathematica, so I haven't tried it).

Hoping you get answer to this. I have the same question.