Martin was upset when, in season six of the television series, the origin of the White Walkers - formerly-human ice creatures - was revealed
"Game of Thrones," the fantasy epic imagined more than 20 years ago by author George RR Martin, will have its much-anticipated finale on HBO later this year.
But in a strange twist never before seen in literature, Martin will himself discover the on-screen ending of his long-running masterwork before he has had a chance to conclude the fantasy on paper.
"Obviously, I wished I finished these books sooner so the show hadn't gotten ahead of me," Martin said recently in an interview with Entertainment Weekly before the final season begins airing on April 14 on HBO. "I never anticipated that."
When the Emmy Award-winning television series about noble families vying for the Iron Throne was launched in 2011, the American author had only written four of the seven books that make up his "Song of Ice and Fire" saga.
His fifth novel, "A Dance With Dragons," was published in July 2011, a few weeks after the end of the first season.
But since then, book fans have eagerly been awaiting the last two novels - "The Winds of Winter" and "A Dream of Spring."
The plot lines for both have already been adapted to the screen based on outlines Martin discussed with screenwriters David Benioff and Dan Weiss on how he foresaw the end of his saga.
"This is simply unprecedented," Nicolas Allard, a French author who wrote a book about "Game of Thrones," told AFP.
He noted that while British author JK Rowling sold the film rights for the first four "Harry Potter" books to Warner Bros, she was able to write the ending of her saga before it hit the big screen.
But in Martin's case, Allard said although the author had given "Game of Thrones" screenwriters a rough idea of how he envisioned the ending, it is unclear whether the show will stick to his story line.
"I haven't read the (final season) scripts and haven't been able to visit the set because I've been working on 'Winds,'" Martin told Entertainment Weekly. "I know some of the things. But there's a lot of minor-character (arcs) they'll be coming up with on their own.
"And, of course, they passed me several years ago. There may be important discrepancies."
Different ending on paper?
According to several experts interviewed by AFP, Martin is not bound by the television story line and he may well choose to depart from it.
"His contract stipulates that he has to come up with the denouement for the series and provide an outline of what would happen," Allard said. "But he is free to choose a different ending on paper.
"And that would be the first time this would happen in the literary world."
He said for example that Jon Snow could very well die of his stabbing wound in the next novel rather than be resuscitated as was the case on screen.
For Sarah Mesle, assistant professor of writing at the University of Southern California, it's all but guaranteed that Martin will move away from the television storyline.
"Even if he sticks to the same series of events... there's no way he can be in the world and not know the way that the audience has responded to the different plot points or the way that we came to love some characters and not others," she told AFP.
"I mean he's... been very much a part of the fan culture of the show, and I think his sense of how audiences feel about his story will certainly affect his choices."
Allard noted as an example that Martin was upset when, in season six of the television series, the origin of the White Walkers - formerly-human ice creatures - was revealed.
"He wanted to be the one to reveal that in his novels," Allard said. "Now, it's like the television series and the novels are two separate artistic elements."
Mesle says it is clear the television series has overtaken the story line and upstaged Martin.
"All of a sudden we have this TV show that has the storytelling status over a book," she said.
"Whether Martin finishes the series or not, once the TV show started to surpass the novels, the novels are now going to be an adaptation of the TV show," she added. "There's no way around it."