No one can ever fully explain why a novel becomes a best-seller and is taken to the nation's heart.

Wolf Hall, at first sight, was an unlikely triumph. It wasn't as if Hilary Mantel was new to the scene, her voice entirely fresh. Nor was the subject. If anything, readers were growing jaded with fiction set in Tudor times. Had her equally tombstone novel about the French Revolution - A Time of Greater Safety - become a runaway success, it would have made more sense. But had that been the case, the resurgence in 16th-century fiction that Wolf Hall sparked would have left our bookshelves thinner.

Barely had Wolf Hall appeared than it was being snatched up and discussed. After winning the Man Booker prize, which added immeasurably to its allure, not to have read it, in certain circles, was social death. Those who could not finish it or grew annoyed with its elliptical style confessed as if to a priest, shamefaced and humbled.

What, then, is its appeal? Most obvious is the novelist's voice and language, as she enters whole-heartedly into the soul of Thomas Cromwell. It did no harm, of course, that the court of Henry VIII is like a doll's house for a novelist, a place of many rooms, packed with colourful inmates with which to fill them. But it was far more than this. Mantel has spoken of the hallucinatory feeling she gets while writing, and this immersion in her character is infectious. Those who slipped effortlessly into her prose were, you might say, mesmerised.

As she told the story of the low-born Cromwell rising to become Henry's most trusted adviser, Mantel overturned the popular presumption that Thomas More was the hero and Cromwell the villain. It is always invigorating being shown a new angle on well-known facts.

But what really cemented Wolf Hall's place in the reading public's heart was something less obvious. One reviewer described it as "a dark mirror held up to our own world". Published in 2009, when we were reeling from years of political turmoil, terror and war, and heading into what looked like a financial abyss, Wolf Hall landed in the laps of readers well-versed in power games and deceit, in matters of life and death, and personal ruin.

This, arguably, is the novel's trump card. Like much historical fiction, it could be read as reflecting the reader's own age. More importantly, given the particularly troubling and sinister tale it told, its readership was already primed. Wolf Hall was intelligent escapism for difficult days. Offering a glimpse of more dangerous times, it allowed a sophisticated form of literary schadenfreude to work its magic, all the while reminding readers that the world and its leaders and the way we are governed has not changed as much as one would perhaps like.