At https://www.chessable.com we manually, line by line, imported a full chess book to our digital format! Takes ages... later, after some validation, we built a tool that automates most of this.
Interesting, I expected this was a manual process. After all, the author has to manually write it the first time round, and inputting the moves takes only a tiny proportion of the time spent writing a chess book. And there are only (a few dozen? A hundred?) books that have been ported from hard copy to Chessable, so there isn't a huge degree of scale.
