IT IS A PARADOX THAT, while children’s fantasy writing has soared in public esteem, fantasy for adults remains in a ghetto. With our leading imprint of fantasy, Voyager, celebrating its tenth anniversary this month and the genre dominating British and US fiction lists, the time has come to ask whether it should be put away with childish things.

“I see all fiction as escapist,” Robin Hobb says. “I’d say literary fiction is a sub-genre of fantasy, trying to mimic real life at its most depressing and oppressive. I’m mystified as to why people think fantasy is only for children.”

The author of a nine-volume sequence that has been compared, justly, with the works of Tolkien and Ursula le Guin, Hobb is one of the great modern fantasy writers. Yet still she remains below the literary radar.

Hobb shares with le Guin the gift for thinking through the logical implications of what a world would be like if magic existed, and for writing about it in clear, vivid prose. Her fantasy world has a Shakespearean flavour, for Fitz, the narrator and hero of the Farseer trilogy, is a royal bastard who must survive in a court very similar to that of King Lear. In addition to the Machiavellian scheming of his relations, he is burdened by inheriting magic skills that must be kept secret.

Witches and wizards have always had animal familiars, but Hobb makes this bond as passionate as the deepest romantic love. The closer the compassionate, agonised Fitz gets to his wolf, Nighteyes, the farther he must travel from human society. Love and slavery, secrecy and honesty are woven into a compelling series that predates many aspects of Margaret Attwood’s Booker-winning The Blind Assassin, and Michelle Paver’s best-selling children’s novel, Wolf Brother. Yet what makes Hobb’s novels as addictive as morphine is not just their imaginative brilliance but the way her characters are compromised and manipulated by politics.

Hobb looks like a nice, middle-class grandmother from Seattle (which she is), but her childhood is straight out of America’s pioneering past. In the 1950s her parents moved their six children from suburban California to a log cabin in Alaska which had no electricity or running water. Within weeks, a half-wolf had moved in. This was Bruno, the inspiration for the intense relationship between Fitz and Nighteyes that develops over five books. Hobb is a keen observer of the natural world — her idea that dragons might hatch out of sea-serpents came from noticing dragonflies metamorphosing in a pond — and her new novel, Shaman’s Crossing, sets the powers of natural against the rigidly logical culture of the Army.

Like all the best fantasy, her subjects address topical events at a tangent. Shaman’s Crossing (set in a different world from that of the Farseers) has uncomfortable echoes of the Iraq War. I ask her whether the Specks, the natives whose ambiguous green goddess ensnares Navarre, her hero, are good or bad. “They’re neither: they’re people,” she answers, pointedly.

Furthermore, they are people the reader can believe in. Where most fantasy fiction is written as if translated, Hobb’s prose has the sinewy simplicity close to that of the myths and fairytales that her English war-bride mother told the family during those long Arctic nights.

She married her husband, a marine engineer, at 18 and while pregnant she started a long apprenticeship writing for children — which she describes as “excellent training” — before writing SF under her real name, Megan Lindholm. Her husband does not read her work (preferring anthropology) and she compares it with cookery or gardening as a hobby done in her spare time between raising four children. Yet she writes prodigiously, seven days a week, even doing it longhand when travelling.

“I can’t wait to get back to writing,” she admits. “You know that wonderful feeling when you really, really enjoy reading a book? Well, for me writing is almost identical to that sensation.”

Such productivity results in an 800-page novel a year — close to the Victorian triple-deckers that her fiction, preoccupied by old-fashioned conflicts involving duty, love and family honour, often resembles. She maps out each trilogy long before she begins to write it, while remaining surprised by how certain characters (such as the Fool in the Farseer trilogy) develop.

Hobb writes about subjects she has questions about, “looking at questions from all sides,” and it is no surprise to learn she is a practising Catholic. In Fitz’s country, people have Puritanical names such as Patience or Chivalry, and these qualities are tested in the course of plots involving regicide, slavery and, inevitably, the quest for dragons.

Her characters age, change, waver and suffer lasting scars, while reanimating the clichés of fantasy fiction. When Fitz tells us that “death isn’t the opposite of life. It’s the opposite of choice”, you feel that his knowledge is real, and hard-won. The opposite of escapist, this is grown-up fantasy that defies both its packaging and the genre in which it is ghettoised.

“Doing your taxes, that’s real,” she says. “Any other imaginary life you step into, that’s fantasy.”

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