So if you know a book that has the information you need, you just need to upload it into the model to get the right answer.
Isn't that a bit circular - if you already know the authoritative source, why ask a model?
It's basically a fancy context aware ctrl-f to the book.
I use this regularly with RPG manuals. I _know_ the stuff, but don't remember every detail by heart. And just ctrl-f:ing through a Mörk/Pirate Borg -style PDF isn't really productive (they're "artistically" laid out). But I can just ask an AI bot that has the pdf indexed like "how does the medical kit work?" and it'll give me a summary along with the relevant rolls within seconds.
Some of the more widely spread and tolerated LLM outputs seem to be AI slop replacing Journalism/Blog slop. Places where people complained about quality already, but tolerated it if important enough.
So to name some of the more common ones Translation, Summarization, and Reiteration of a source material.
Humans put spin on things, how much you trust a source might not reflect the source's factual accuracy. It might just mean you liked reading it better from one source than another.
Because it's faster.
I've done this on different topics - I know the answer is in a particular eBook/PDF/document, but for whatever reason it's not trivial to look it up. The model can do it a lot more quickly than I can, and then I can still verify the accuracy.