Even if the smart money for the overall Costa Prize is still on Hilary Mantel, who won the novel category for Bring Up the Bodies last week, the fact that a comic book by the husband-and-wife team Mary and Bryan Talbot won the best biography award carried more than a little significance.

The couple's graphic memoir Dotter of Her Father's Eyes, which interwove Mary Talbot's life story with that of James Joyce's daughter Lucia, saw off Artemis Cooper's 400-page life of Patrick Leigh Fermor and Kate Hubbard's study of Queen Victoria's servants to become the first comic – or graphic novel, to use the acceptable marketing description – to win a major literary award, much to some commentator's chagrin. Giles Coren in the Spectator, for example, suggested when the shortlists were announced that the judges were just trying to be hip.

Of course, if that was the case they wouldn't have chosen such an obviously "literary" graphic memoir and would have given a prize to the other comic shortlisted for the Costa Prize, Joff Winterhart's plain, poignant and at times laugh-out-loud funny Days of the Bagnold Summer, over Mantel in the novel category.

But the success of the Talbots' book is a marker that the literary establishment has finally warmed to the graphic novel. It may also provide a way in for new readers to an artform that has been steadily on the rise for the last 30 years.

It was the publication of Art Spiegelman's holocaust memoir Maus back in the early 1980s that first showed the wider literary world what could be done in the humble comic-strip form. It coincided with a darker, more adult approach to superheroes by writers such as Frank Miller and Alan Moore in Dark Knight Returns and Watchmen. But the inevitable "Comics Have Now Grown Up" headlines that resulted proved a little premature. It needed another three decades for comics to build up a critical mass of material to prove superheroes were not the only genre at which comics could excel.

Yet 2012 seemed in many ways a banner year for comics, with significant publications by mainstream publishers such as Jonathan Cape and Faber, complemented by books from small, bespoke UK publishers such as NoBrow, Blank Slate and Self Made Hero. Chris Ware's astonishing and innovative graphic novel Building Stories deservedly made many "best-of-the-year" lists, while Joe Sacco's Journalism proved comics could work as a vehicle for investigative reporting. Closer to home, cartoonists such as Luke Pearson and Simone Lia showed there was a new generation of cartoonists coming through as well. No surprise, then, that Bryan Talbot, a veteran of the underground comix of the 1960s and 1970s and a sometime artist on Judge Dredd, said after his Costa Prize win: "We are living in the golden age of graphic novels. There are more and better comics being drawn today than ever in the history of the medium and there's such a range of styles of artwork, of genre and of subject matter."

At the same time we've also seen the demise in print last month of The Dandy, leaving only the Beano and 2000AD to carry the flag for British comics not linked to a TV franchise. From the outside you could argue that comics have now left kids behind. But that's not right either. Not only have cartoonists been stretching the form for adults, but there are comics and graphic novels emerging for kids as well. Luke Pearson's Hilda books are happy to admit their debt to Tove Jansson while Glasgow-based duo Metaphrog created a comic world that is suitable for both adults and children. Meanwhile, NoBrow has announced it is launching a children's imprint, Flying Eye Books, next month.

How golden this era is, of course, may depend on how far the literary establishment is prepared to go with its newfound love of the graphic novel. I guess we'll know the answer if one makes the Booker longlist later this year.