Jaws of the Six Serpents is a Medieval-type fantasy genre world for the free PDQ game system. The PDF / book has a very nicely-done layout and wonderful artwork to accent the information.
While the setting is very detailed, it tends toward a darker vision of magic, so if you are looking for a fantasy game world that is a little more "light hearted" then JOSS is not for you. Save your 10 dollars.
If you don't mind that aspect of the book, then JOSS is a decent choice for the PDQ system, even at around 10 dollars (dark fantasy is just not my thing).