I can confirm that both of these are great if you like either puzzles or rogue-likes, respectively. Simon Tatham’s Puzzles is easily my top played mobile game.

Calibre is the main program for doing most things with ebooks. It’s plug-in support allows for things like deDRM that you can use for stripping DRM. There are a lot of tutorials out there for it.

If you read the caption on the photo it says that it is of a sign in German at a Texas children’s hospital.