This series of decks is, by far, the most used and most useful accessory I use in my games. When I run a game I lay out 4 or 5 so i can reference them discreetly (for example, when i need an NPC name or a location description). When I play solo games this is a fantastic all-in-one tool. I definitely recommend getting all of the themed decks, but starting with this basic set will give you a lot of mileage.