Thanks for the feedback. One of the features allows users to upload an epub to use in the app. Although I realise that a better method is needed, as it has become harder to find legitimate places to buy epub formatted books.
That said, I'd gladly pay you/the site to handle that for me (by paying more than the book's retail price). Hopefully the translation would also be better than anything I imported.
(Two sibling replies linked to sites that sell technical non-fiction. That is a very hard way to learn :-) )