Random House has released a companion app for George R. R. Martin‘s Game of Thrones books series.

The app, which is called A World of Ice and Fire, is an official guide to the series and includes biographical profiles of the epic’s 540 characters, descriptions of the 380 locations from the stories, as well as interactive world maps.

The app is designed with anti-spoiler shields, so that readers can customize where they are in the book and only explore the worlds that have been revealed to that point. Elio M. García Jr. and Linda Antonsson, the founders of fan site Westeros.org have written original text for the app.

Apple has it available for free with in-app purchases available. The free edition includes eight character profiles from A Game of Thrones, as well as interactive maps for the North and South. Readers can buy additional InfoPacks based on each book for $.99-$1.99, depending on the title, or the entire pack for $4.99. Nook is offering the entire app for $4.99.