Have a look at Factorio. It’s DRM free and you can easily spend hundreds or thousands of hours on it if you like it. Try the free demo first. Also keep in mind that it’s never on sale (or always, depends how you look at it). Be warned though, it’s very addictive.

Thanks

Thanks, it would never occur to me to look for it on Wikipedia.

Is it on a stable website, or does it change sometimes? And what’s the address?

I use Pocketbook. It opens just about anything - epub, mobi, pdf, pdb, and many more formats. Just get a book anywhere and copy it via USB. Or send it as an email attachment to your special address and it will download automatically. You can even replace the reading app with another relatively easily, if you want.