Originally, Mr. Martin only had a single R (standing for "Raymond") separating his first and last names. After his confirmation, he added the second one (standing for "Richard"), in a rare instance of Martin adding characters without brutally murdering any to keep things even.
In November 1963, a young 15 year-old George Single-R Martin had one of his first pieces of writing published - the above fan letter to Fantastic Four creators Stan Lee and some other guy (KIDDING - it's Jack Kirby, the creator of Nintendo's Kirby series and literally nothing else). This is the issue li'l Georgie's referring to:
Martin's only complaint was that the Human Torch wasn't brutally stabbed through the face with a rusty sword as The Thing was tortured for 9 issues straight.
Long before the first novel in the A Song of Ice and Fire series (Game of Thrones) was published in 1996, Martin started a multi-author anthology series called Wild Cards in 1987. Wild Cards concerned an alternate history, starting right after World War II - an alien virus covers New York City and wipes out 90% of the population. The remaining 10% are alive, but changed - 9% become horribly mutated monsters, and 1% gain superpowers. The ones with superpowers (called "Aces" - except for those with useless or silly superpowers, known as "Deuces") largely don't wind up as crime fighters like Superman, but rather follow plotlines that flow much more realistically from these new circumstances.
And yes, there IS a lot of sex and graphic violence.