Tunic uses the idea of a video game manual in such a wonderful way. Its not just a “hey this is what the buttons are, the interface is and a couple of character bios” kind of manual. The devs have made it a core part of the games experience as it guides you through literally the whole game and its secrets without even telling you that’s what it’s doing.
If you’ve not played it you need to experience it for yourself, it’s brilliant.