It's a smaller, edited set with fewer cards (112 cards vs. 168), that only supports 3-4 players.* They did this so it would fit in their standard two-deck expansion tuckbox (and stockings hung with care!), as well as making the price super-reasonable. But it's still a completely playable version of the game.
We also stripped down the rules: for instance, there's no Death, no Undead rule (although the Santa rule takes its place), no Super Munchkin or Half-Breed, and no Big items. We also took out all the "usable only by X" and "not usable by X" cards.