I've done something similar myself with Kindle Cloud Reader a few months ago. For the purpose of language learning, I wanted to extract the surrounding context of every word I highlighted in books I read. Turns out it's impossible only with the device.

On Kindle Cloud Reader, Amazon serves images for the pages of the book, so you can't directly read the text. But you can indeed OCR the images and extract the context like that. I created a small browser extension with Claude.

It's crazy how difficult Amazon made this process for reasonable use cases like that.

is it impossible now to crack the file directly to get all of the books text out? there used to be a few ways to decrypt them in calibre and similar