Sunday’s season 3 premiere of Game of Thrones drew in 4.4 million viewers, so naturally HBO renewed it for a 4th season. Game of Thrones is easily one of HBO’s highest rated shows; after repeats the premiere of season 3 pulled in 6.7 million viewers.
Each season of the show is adapted from one of the books in George R.R. Martin’s A Song of Ice and Fire series. Season 1 is adapted from the first book A Game of Thrones, season 2 from A Clash of Kings, and season 3 is roughly half of A Storm of Swords. Season four will finish the off A Storm of Swords.