You cannot change a pokemon game’s language in the middle of a playthrough. You choose the language at the very beginning of the game. This is because a breeding pair of Pokemon with different language origins have a higher chance to breed with each other and produce eggs faster - I think the eggs may also have a higher chance to be shiny, but I’m less sure of that. Either way, it’s supposed to motivate you to trade online.
If you wanna change your language, you’re gonna have to wipe your save and start over.
How about a project Gutenberg “best of” CD full of free public domain ebooks?
Download page: https://www.gutenberg.org/ebooks/11220 Link directly to download: https://www.gutenberg.org/files/11220/PG2003-08.ISO
They also had a dual layer DVD download if you want something bigger. They don’t seem to host it anymore, but archive.org does.
https://archive.org/details/pgdvd042010