George RR Martin has revealed that he has found it hard to finish the long-awaited sixth book in his A Song of Ice and Fire series, as the rise in fame and popularity that came with the television adaptation Game of Thrones has become a “considerable weight to bear”.

In an exclusive interview with the Guardian ahead of the publication of his next book, Fire and Blood, a history of the fantasy universe of his hugely popular series, Martin said he’d been wrestling with The Winds of Winter, which has been eagerly awaited by fans since the last book in the series, 2011’s A Dance With Dragons.

“I’ve been struggling with it for a few years,” he told the Guardian. “The Winds of Winter is not so much a novel as a dozen novels, each with a different protagonist, each having a different cast of supporting players, antagonists, allies and lovers around them, and all of these weaving together against the march of time in an extremely complex fashion. So it’s very, very challenging. Fire and Blood by contrast was very simple. Not that it’s easy – it still took me years to put together – but it is easier.”

He confirmed that the sixth instalment was his next priority: “The Winds of Winter is next, then I’ll decide what comes after that – whether it’s to go on to A Dream of Spring, the last one, or whether I switch back into Fire and Blood II, do another Dunk and Egg story or two. But I’ll worry about that one thing at a time – that’s too far ahead.”

While Martin’s books were bestsellers before the HBO adaptation Game of Thrones in 2011, the overwhelming success of the television show saw his readership increase by millions. The TV adaptation, which has won 47 Emmys and a Golden Globe over seven seasons so far, overtook Martin’s progress in the book series in 2016, and is set to conclude next year.

Once I get rolling, I don’t care what my email says or who’s mad at me this week because The Winds of Winter isn’t out

In the interview, Martin revealed that the success of the show had left him feeling under even more pressure to finish writing the series, which is set to end with the seventh book, A Dream of Spring. Irate fans have long pestered the 70-year-old author for updates. In a 2014 interview for Swedish TV, he said that fans worrying that he would die before finishing was “pretty offensive” and gave them the finger; meanwhile fellow fantasy author Neil Gaiman pronounced to an angry Martin reader online: “George RR Martin is not your bitch.”

“The show has achieved such popularity around the world, the books have been so popular and so well reviewed, that every time I sit down I’m very conscious I have to do something great, and trying to do something great is a considerable weight to bear,” Martin said. “On the other hand, once I really get rolling, I get into the world. The rest of the world vanishes, and I don’t care what I’m having for dinner, what movies are on, what my email says or who’s mad at me this week because The Winds of Winter isn’t out – all that is gone and I’m just living in the world I’m writing about. But it’s sometimes hard to get to that almost trance state.”

In the last year, five potential Game of Thrones spin-off shows with HBO have been announced, with only one having been greenlit so far: The Long Night, which will be set 5,000 years before Game of Thrones and written by Jane Goldman. Martin confirmed they were all prequels, but said he did not expect all of them would be made and that he was not writing any of them. “None of them are traditional spin-offs,” he said. “You won’t be seeing the further adventures of Arya, Sansa or Jon Snow, you’ll be going back in time. The other four are all over the map and at least two of them are solidly based on material in Fire and Blood. Those haven’t been greenlit yet.”

