In Playing a Book, I said:

You don’t read a programming book, you play one. I mean play, like playing a game. In a game, you progress through levels by learning and applying skills. At the end of the level, you play against a boss that you have to beat to progress.

I want to clarify that I don’t mean “Gamification”. I don’t want a book to seem like a game—I want it to literally be a game.

In a gamified book, you would just write the book as normal and then give the user a badge when they complete a chapter. Or maybe you’d assign points to various things.

The distinction I am trying to draw is that playability is something you start with to drive your design. Gamification is something you slap on at the end.