I've been using Gemini-1.5-Pro-2M through Poe for creating e-book recaps and just generally interactively jogging my memory about a prior entry of a book in a series when a new one comes out. It's been working surprisingly well, even for very large books.

Gemini Advanced seems very promising with 1 Million token context window.

https://one.google.com/explore-plan/gemini-advanced

I haven't tried it as I use Claude primarily.

aistudio.google.com by far. It would handle 10000 pages for free or even more with it’s 2M context window.