William Hogarth, the 18th-century painter, gives Old Father Time a speech bubble for his last gasp, with the word finis inside it. Hogarth remains secure in the bosom of high-brow culture, but the speech bubble has been viewed throughout this century as a lower literary form - cheap, for the semi-literate - or the playful subject of pop art.

Comics have traditionally been under-appreciated in Britain and even blamed for some of society’s ills, but now their potential is being tapped both as literature and aids to literacy.

Graphic novels with their comic format, sequential frames and speech bubbles are finding their way into mainstream bookshops and libraries. They have some formidable champions. Philip Pullman, the novelist and Carnegie Medal winner, has been trumpeting their cause for the past 10 years.

As evidence of the new-found respectability of the comic strip, there has been a conference, Frame Up! Comic Cuts to Literacy, at the Centre for the Children’s Book in Newcastle upon Tyne, and a World of Tintin exhibition at the Science Museum, moving on next week to the North-East where it will be supported by a Centre for the Children’s Book programme of debates. Herge’s moral and political philosophy, as encapsulated by Tintin, is also being reassessed, but the quality and beauty of his graphic form is not disputed.

It is 70 years since Herge’s comic strip about Tintin, the intrepid boy reporter, and his faithful dog Snowy, first appeared in the newspaper supplement Le Petit Vingti me. Since then the standard editions of the Adventures of Tintin series (21 tales) have achieved sales of over 200 million in 58 languages. To celebrate the anniversary, Egmont Children’s Books, whose imprints Methuen and Mammoth have been publishing in English since 1959, has added the first Tintin story, Tintin in the Land of the Soviets, to the Adventures series. Although this early work seems crude and clumsy when compared with Herge’s later titles, the meticulous reality with which each panel is drawn, his impeccable sense of comic timing and his grasp of working anatomy is all there.

Mammoth has also published two new titles in its Epix series of graphic novels which matches graphic artists with top children’s writers and is popular with older primary readers. The Thing that came from Jason’s Nose! has echoes of Raymond Briggs’s Fungus the Bogeyman in its witty account of how one of the infamous bogeys from the weediest boy in Carpenter Street School takes on a monstrous character when it finds its way into sewers contaminated by a radiation leak from a nuclear reactor. The graphic frames in both this and Animal Avengers are lucid and inventive, constantly shifting focus and perspective with a dynamic variety of line and tone.

Children who have enjoyed Epix can join adolescents and adults in appreciation of JLA Year One, a clever and captivating re-visiting of the post-war Justice League of America stories, a contemporary take on comic super-heroes which is as much about saving the developing world as the civilised West.

Instead of the straightforward tales of victory when Batman, Wonder Woman, Superman, Flash, Green Lantern, Aquaman and the Martian Manhunter teamed up against a never-ending sequence of alien threats, we are presented with a new story in which the JLA explores its history and character with a thrilling retrospective. Indeed these stories peer behind the heroic facades of the characters to reveal an angry loner, a cautious philosopher and a second-generation vigilante out to prove something to her mother.

The graphic range of this book is breathtaking, the narrative multi-layered, the drawing highly polished, and the language is challenging and requires fluent readers. Note this soliloquy by Martian Manhunter: “For years I have been stranded on a world not my own, one that has a history of being unreceptive to those who are different.” He speaks of having survived by “chronicling information on the motivation of the strangers around (him)”.

For a definitely 16-plusadult read, The Dreaming: Through the Gates of Horn and Ivory extends Neil Gaiman’s acclaimed Sandman series in a mystical but often macabre exploration into an almost metaphysical landscape “where the lines of fantasy and reality blur”. This is a complex and literary book, marked by richly informed illustrations, and shows the graphic novel at its most sophisticated.

The World of Tintin is at the Science Museum, London to July 11 and at the Discovery Museum, Newcastle in association with the Centre for the Children’s Book from July 15 toSeptember 5. For details of events,call 0191 230 4220 from July 12.