I had this use case also in mind. Already tried with one book, but the results were not that good. Many of the tables and text boxes were messed up. I had pretty good results converting tables to markdown with ChatGPT by taking a screenshot of a table and pasting it to chat. It was able to handle some "irregular" tables with a bit of prompting. Like "Read the table row by row. Column headers are X, Y, Z. X is text, Y is number, Z is word" as a simplified example.