I don't understand the point of buying an eBook with DRM. I'm going to run into an issue trying to get it to work on one of my devices at one point or another. The lack of a DRM-free option is what would tempt me to piracy.

And can you point to a single piece of media which has never been pirated, DRM or no?

Having it be DRM-free means he doesn't have to mess around with every store under the sun. I'm not a Google Play user normally, but this lets me purchase it through the web interface, download the PDF, and then read it however I want. For his book on Wolfenstein, I did just that by reading it in Apple Books on my iPad.

What format is the book in? A regular PDF isn’t as good in Apple Books, for example. Taking notes, night mode, bookmarks, ...

> What could be some reasons behind him doing so?

Giving his readers the ability to read the book without requiring them to install proprietary software.

It might be pirated, but probably not very much. First, a book PDF is probably 100MB or more, so too big to email. Second, it's a niche market, so there probably won't be enough seeders for a decent torrent. Third, it takes some amount of effort to host a copy on the web, and there's very little benefit in doing so.

If it's digital it's going to be pirated regardless the DRM attempts .

Some people like to share knowledge more than they like (or need, seeing the numbers) to make money.