The ending of Game of Thrones produced a storm of criticism from devoted fans, with many attacking it as anticlimactic end to a final series. A petition demanding that the HBO channel reshoot it from scratch has now been signed by more than a million viewers.

But the series’ creator, George RR Martin, has insisted that the furore over the television adaptation of his fantasy novels won’t change what he writes next.

In a rare interview with the Observer, Martin said that the TV show had not been “very good” for him and admitted that he found it being over “freeing”. He still has two more novels of the fantasy saga to write, but insisted their endings would be unaffected by the controversy over the show’s ending.

“No, it doesn’t. It doesn’t change anything at all … You can’t please everybody, so you’ve got to please yourself,” he said.

Martin published A Game of Thrones, the first in a planned seven-part series called A Song of Ice and Fire, in 1996. It was adapted by HBO for broadcast in 2011. Thanks to the combined success of his books and the show across the world, Martin, 70, is estimated to be worth $65m (£54m). But, he said, his increasing fame had made writing difficult.

“I don’t think [the TV series] was very good for me,” he said. “The very thing that should have speeded me up actually slowed me down. Every da]y I sat down to write and even if I had a good day … I’d feel terrible because I’d be thinking: ‘My God, I have to finish the book. I’ve only written four pages when I should have written 40’.”

Martin said he would “let fans have their theories” but that he now steered clear of the intense emotional response the show provoked online.

“I took myself out of all that,” he said. “Some of [the theories] are right and some of [the theories] are wrong. They’ll find out when I finish.”

George RR Martin says: ‘I don’t think [the TV series] was very good for me.’ Photograph: Antonio Olmos/The Observer

Martin spoke fondly of interactions with fans of his books, but said he was unable to attend the GoT conventions as he once did.

“I don’t want to go to a party where an unending succession of people want to take selfies with me,” he said. “Because that’s not fun the way it was in the old days. That’s work.”

When asked whether he missed the early days, the author said: “Yeah, honestly I do. I mean, I can’t go into a bookstore any more, and that used to be my favourite thing to do in the world. To go in and wander from stack to stack, take down some books, read a little, leave with a big stack of things I’d never heard of when I came in. Now when I go to a bookstore, I get recognised within 10 minutes and there’s a crowd around me. So you gain a lot but you also lose things.”