World Maker is a single-player world-generation game.
It's 10 pages with great, readable layout, but no major illustrations, and it uses a deck of playing cards for randomization.
Surprisingly, World Maker feels almost better tailored to setting up novels. It allows you to randomize genre, randomize and randomly flesh out central characters, and then it has you figure out the connections between your characters---and in doing so establishes the setting.
I think World Maker is a heck of a utility if you write NaNo. There's no fussing over what your novel's going to be about. You just pull some cards, make some decisions, and you're off.
As a game design toolkit, though, I think its helpfulness depends on whether you like building settings around characters, or building settings without worrying about characters. World Maker starts with characters and works outward, so any game you build from it is going to have a few *very* important NPCs at its heart.
Overall, if you're a writer who likes to improvise or a GM who likes to build your settings around certain core characters, get this. If not, it's still a good way of putting together complex NPCs, and I'd recommend picking it up for that.