Sounds like a cool project. Not sure if it's one that I would personally use, but I think that LLMs can be used wisely.

What I've found interesting when doing similar experiments (feeding things like books to an LLM and asking questions) is that the output is almost always more bland than one would hope for. I suspect this may both be a result of LLMs being biased for the material they've been trained on and a reality I've suspected which is that the majority of books are mostly filler and aren't making points that are particularly profound. Most books, when you distill them down, fundamentally communicate ideas that are rather obvious, but the language around those points makes them sound a lot more profound than they really are. It's a kind of hypnosis, I think. In a sense, LLMs may be able to reveal how bereft a piece of written material is.

I disagree with the OP's statement that traditional e-readers being passive is actually a "problem". It's kind of like saying that cars are a problem because they can't fly. Maybe I'm being pedantic, but being alone with a book and one's own thoughts is hardly a problem; if anything, the problem is fewer and fewer people are comfortable without a constant barrage of thoughts other than their own.