TV show A Game of Thrones has been a big hit around the world, sparking renewed interest in the books that it’s based on. Now there’s a companion app for them.

George R. R. Martin’s A World of Ice and Fire – A Game of Thrones Guide is a freemium app for iPhone and iPad, published yesterday by Random House Digital.

Aimed at viewers of the show as well as readers of the books, the app promises profiles of more than 540 characters (Count ‘em! Actually, don’t…) alongside interactive maps of the Game of Thrones world.

A smart inclusion is “anti-spoiler functionality” that involves telling the app where you are in the story, to avoid seeing plot giveaways.

We said this is a freemium app, so how does that work? The initial download includes some character profiles and a couple of maps, but you then buy ‘InfoPacks’ for each of the five books in the series at $0.99 each.