The object of the game is to score a pre-set amount of Adventure Points before any of the other players. Players build their adventuring party by playing Character cards and arming their characters with Stuff cards. The characters come in a variety of fantasy races and character classes. The adventuring party's strength is determined by adding together all of the Character Points each of the Character and Stuff cards are worth. Character cards' point totals can be affected (positively or negatively) by event cards that can be played on them.
When an Adventure card is played, all of the players compete for the card's Adventure Points in an Adventure Round. In this round, players can enhance their party's Character points total or degrade their opponents' by playing Encounter cards. Once all of the Encounter cards have been played and their effects taken into account, the players add their total Character points and roll a six-sided die. The player with the higest total wins the round and the Adventure Points listed on the Adventure card. Some Adventures will also award additional Stuff cards.
Characters that are wounded or Stuff that has been used are flipped, changing their point total. If the card is flipped again, that card is discarded. Players can unflip flipped cards by discarding cards and taking no other action that turn.
The game plays very fast, and there is a good amount of strategy involved when building and equiping your adventuring party (or messing with other players' parties...). Due to the multiple character and stuff combinations, the replay value is very high.
The full-color art is all done by Dan Smith in Dan's cartoony style. The card art matches the humorous tone of the game perfectly, and it is neither too large to be obtrusive, nor too small to be ineffective.
The game that Portable Adventures: Lair of the Rat-King best compares to in terms of theme is Steve Jackson Games' Munchkin. Portable Adventures is quicker to play, deeper in strategy, and more replayable than Munchkin. It's not nearly as silly as Munchkin, but it still has plenty of humor. While the artwork of Portable Adventures is good, the art isn't meant to be the central selling point of the game. (How popular would the Munchkin games be without the excellent Kovalic art?)
What's more, the game is truly multi-genre. When you jump from the Lair of the Rat-King to, say, the 8th Grade (the other Portable Adventure set that's currently available), there's a reason for it. A trigger card will launch your game into a whole new world of adventure.
If you're looking for a quick game of adventuring but you don't have the time or enough players for a full RPG session, Portable Adventures: Lair of the Rat-King is an excellent choice. Or, Lair of the Rat-King can be combined with any (or all!) of the other Portable Adventure genre sets for an evening of multi-dimenisional fun!
Highly recommended.

