[whswhs]

GURPS Dungeon Fantasy is a set of rules for running campaigns in the style of D&D, but using GURPS mechanics.

GURPS Fantasy is not so focused on rules; it's more a guide to the fantasy genre, and especially the genre of historical fantasy (fantasy set in societies of the past, or in invented worlds with similar technology and institutions). It doesn't talk a lot about dungeon fantasy, and tends to subsume it under "sword and sorcery." It looks more at high fantasy (close to mythology), low fantasy (close to realistic fiction but with magical/supernatural elements), light fantasy (comedic), and dark fantasy (close to horror). It discusses the kinds of things you find in these—the supernatural, worlds, creatures and races, history, locations, magical arts—and gives examples, but not a comprehensive treatment of any of them. It ends with a campaign setting, Roma Arcana, the Roman empire with magical arts that have begun to cost it the favor of the gods.

GURPS Fantasy is an example of a genre book, like GURPS Horror, GURPS Space, or GURPS Supers; its focus is "how do you do this broad type of work within GURPS mechanics?"