Today George R.R. Martin is famed as the author of "A Song of Ice and Fire," the bestselling fantasy novels that inspired HBO's hit drama "Game of Thrones." But long before he earned his first Hugo Award, and decades before he was dubbed "the American Tolkien," Martin was a devoted Marvel Comics fan and a pretty prolific letter writer.

RELATED: Stan Lee, George R.R. Martin & More Join History's Comic Book Special

His first published letter, written as a 14-year-old living in New Jersey, has circulated online for years now, but on History's two-part special "Superheroes Decoded," Martin actually reads his praise for 1963's "Fantastic Four" #17, which he insisted "will live forever as one of the greatest F.F. comics ever printed. Watch the clip ahead of Sunday's premiere below.

The documentary explores how the rise of the superhero parallels America's own ascent as a 20th-century superpower. The first part centers of the origins of the iconic American superhero, while part two examines the American rebel.

Martin is joined in "Superheroes Decoded" by the likes of Stan Lee, Captain America: Civil War" directors Anthony and Joe Russo, "Iron Man" director Jon Favreau, actor Anthony Mackie and author Brad Meltzer.

"Superheroes Decoded" premieres Sunday at 9 p.m. ET/PT on History, with the second part airing at the same time on Monday.

(via i09.com)