You get 50 cards to add to the various decks of the game, 25 new Job cards and 25 new Supply cards.  There are 5 new cards per deck i.e. 5 new Space Bazaar cards, 5 new Amnon Duul Jobs, etc.  Some of the show specific (while I realize the entire game is show specific, there are generic cards like Merchant and Helmsman) include Elder Gommen, Nandi's Gun Collection, and The Best in the House.  Tabletop games tend toward the expensive side, and thereby expansions/boosters tend toward that as well.  If you have the game, and need a little more variety you've already got this piece of shiny.