“Ho-hum! Another month, another bunch of classics, but then what can else can one expect from you chaps?” begins a letter from the then 16-year-old George RR Martin to Stan Lee and Jack Kirby of Marvel Comics.

The Game of Thrones author’s letter, which was published in Fantastic Four volume one, issue 32 in 1964 and has now emerged online, initially praises Lee’s “sparkling script” and Kirby’s “sublime” art in their latest issue of the superhero comic, but then points out a plot hole.

“I regret to inform you that I found one flaw in this otherwise perfect masterpiece, a flaw that is, regrettably, very common with you. When we last saw the Red Ghost in FF #13, he was stuck on the moon being chased around by three super-powered apes livid with hatred and waving Mr Fantastic’s paralyser ray at him. Now suddenly you bring him back in full control of his apes without one single word of explanation,” the young Martin writes.

‘Wow! Aren’t our faces red!’ … Stan Lee, standing, with Marvel artist John Romita in 1976. Photograph: AP

He goes on to criticise Lee and Kirby for the revival of supervillain the Puppet Master in another issue of Fantastic Four, an event Mr Fantastic inexplicably misses: “Some scientist – can’t even tell whether a chap is living or dead but is bright enough to come up with a super-amplified-cosmic-powered-radio-active-doohickey-ray at a moment’s notice!”

However, Martin closes with some words of encouragement: “In conclusion, I’ll wish you luck on all forthcoming books, but Stan, don’t pull any more returning villains out of your hat. Next time tell us how they remade the scene – OK? OK!”

“Wow! Aren’t our faces red!” reads Lee’s response. “You want the truth, Georgie? We just plain FORGOT where we left the Red Ghost, and didn’t have time to look the issue up because the printer was breathing down our necks with our deadline!”

After going on to become a famous writer in his own right, Martin would later tell the BBC: “Maybe Stan Lee is the greatest literary influence on me, even more than Shakespeare or Tolkien.” In a 2011 interview, Martin acknowledged the influence of Lee’s work with Marvel – for which he created Spiderman, Iron Man, Hulk and the Fantastic Four – on his own writing: “The Marvel characters were constantly changing ... As opposed to DC [Comics], where everybody got along and it was all very nice and all the heroes liked each other … Stan Lee introduced a whole concept of characterisation to comic books and conflict; maybe even a touch of grey in some of the characters.”

Another letter from a young Martin to Lee and Kirby was found in 1961’s Fantastic Four #20 and published on the Marvel Archives, where he proclaimed a previous issue “absolutely stupendous, the ultimate, utmost!”