If you haven't read the books, we also have the entire series (known as The Song of Ice and Fire, Game of Thrones is the title of the first book).
You might also consider some other authors:
Joe Abercrombie - The First Law Trilogy
Glen Cook - Tales of the Black Company
Steven Erikson - Malazan: Revenge of the Fallen (10 volumes, Gardens of the Moon is the first)
Patrick Rothfuss - The Kingkiller Chronicles
Brent Weeks - The Night Angel Trilogy