A Game of Thrones
George R. R. Martin has some very loyal but impatient fans. It's taken him a bit longer than expected to finish (or not finish) this series and fans sure have given him a hard time about it. (Source.)
True story: the audiobooks for the first four books in the A Song of Ice and Fire series were read by British actor (there they call them "thespians") Roy Dotrice, who voiced 224 characters in A Game of Thrones alone. That's a Guinness World Record. No joke. (Source.)
Unlike some other prequels (cough Star Wars cough), A Game of Thrones has some prequel stories that are a lot of fun. Martin has so far written three stories in the "Tales of Dunk and Egg" series (and they're stories, so hallelujah, they're not doorstoppers like his novels).