Two thumbs up for Arkham Horror: The Card game! While it's set in the same universe as the board game, the card game plays more like a coop tabletop RPG blended with Magic the Gathering. Players select a character and then build a deck of skills, allies, gears, etc. to help them tackle each scenario. Each scenario is unique, and many are part of a greater campaign, which allows you to build your character deck with XP points earned for successfully completing objectives. Your FBI Agent, Roland, might start with his trusty .38 revolver and eventually upgrade to a shotgun, some extra ammo, a machete and his trusty .38. Each character offers different deck building challenges, different play styles and different experiences.
If you're familiar with Fantasy Flight's Limited Collectable Game concept, Arkham uses this model as well! If not, Arkham does releases more like an MMORPG than Magic the Gathering. After the core set, a new expansion box is released each year, then scenario packs for that expansion every few weeks, and each pack contains set cards, unlike a random booster pack or deck. You'll need a core set to try the game out (a second when you're ready to start deck building), and each of the expansion boxes contains new characters, new scenarios, and new player cards. Scenario expansion packs build on the campaigns started in each in the expansion boxes, and also include a handful of new player cards as well. There are also stand alone "sidequests" that can be added on to campaigns!
Overall, Arkham is a unique, engaging card game, blending aspects of many different kinds of games into one package.