The Courtesan's Revenge by Frances Wilson<br></br>Courtesans by Katie Hickman

A courtesan's work is never done. Sarah Bakewell discovers a fascinating world of sex, literary blackmail and mice-infested hairstyles

These books both open on scenes of divided light and shadow. Katie Hickman begins with a childhood memory: walking with her grandmother through Montmartre at night, she realized that a beautiful woman was standing inside a doorway near them, half illuminated by a lamp, half invisible in darkness. As they passed, the woman let her black cloak fall aside to reveal a luxurious assemblage of scarlet undergarments; and instead of hurrying her young charge on, Hickman's grandmother insisted they pause to admire the woman's beauty. But it was a strange kind of beauty, for the woman seems to have been uncanny and a little monstrous, like an exquisitely frilled octopus in a reef-wall cave.

Frances Wilson's biography of the famous Regency courtesan Harriette Wilson also opens with a composition in light and dark, this time a landscape rather than a body. From Virginia Woolf's review of Harriette's Memoirs, she borrows the image of a continent divided by a sword's shadow. One side is bright and orderly: the world of decent society, through which a respectable woman walks as if on a path through Kew Gardens. The other is a glowering, tumbled wilderness of precipices and ruins. A man can traverse the whole continent at will, stepping from gloom to sunlight and back - but any woman who once crosses the shadow of the sword can never return to the light.

This crepuscular, divided world, the demi-monde of "High Impures" and their clients, forms the setting for both books. The Courtesan's Revenge focuses on one extraordinary woman, a boyish livewire better remembered for an act of audacious literary blackmail than for her original profession. With her career in decline, Harriette Wilson threw London into mingled panic and delight in 1825 by publishing her Memoirs - as a serial, each instalment containing a list of eminent names which would feature in the next episode if their owners did not pay to have them removed.

Many, like Wellington, simply let her "publish and be damned", although he never actually used those words. The brilliant marketing ploy did not make money, for the publisher was almost ruined by libel suits, but it was certainly a hoot for London society. It also saved Harriette from the usual fate of ageing courtesans: decline into the even shadier world of low-class prostitution followed by early, raddled death. Instead, she reinvented herself as a woman of letters, beginning flirtatious correspondences with authors and making the most of her revived fame.

The Memoirs are a prime attraction in Wilson's book, for her subject's voice comes through persuasively - although the author is careful not to rely too heavily on it as a source. Harriette's style is lively, if unschooled, and she shows a real literary sensibility when she complains that certain words (like "queer") make her feel physically sick. The opening sentence is one of the best narrative hooks in any autobiography: "I shall not say why and how I became, at the age of 15, the mistress of the Earl of Craven." And her account, full of exuberant self-aggrandisement, reverses Woolf's landscape by creating "a timeless world in which she was the dazzling sun and all the great men she had known were mere stars".

The voices in Katie Hickman's Courtesans are equally arresting. She recounts the lives of five legendary English "horizontales", of whom Harriette Wilson is one. Two wrote memoirs - Wilson, and the flamboyant Cora Pearl - and most left eloquent letters and journals. At one stage Hickman speaks of silenced voices, but these women are deafening compared to respectable contemporaries, and she proves this by feisty quotes: "I can never submit to the control of a husband"; "I will be the mere instrument of pleasure to no man."

What does come across is the danger and sheer weirdness of a courtesan's life. They could be grand to the point of high surreality, and were often trendsetters for society, although never quite fit to be seen in public. Their admirers imagined them as bizarre dream beings: among the species conjured by Hickman are phoenixes, chameleons, ghosts and exotic animals.

It was part of a courtesan's professional duty to create this aura of "extravagance and fantasy": there must be exquisite dinners, beautiful clothes, encrustations of jewels, fine stables with high-stepping horses. No one did this sort of thing better than Cora Pearl, who once dyed her dog blue to match her outfit. Artifice itself formed part of the fascination, but there was always the risk of its tipping over into garish horror - the enchanted grotto could become a circus sideshow.

Indeed, the theatricality of the most successful courtesans had to be counterbalanced by a kind of natural, easy sensuality. Beauty was not essential, but sexual confidence was. As Hickman reminds us after conjuring up the fantasy world of Cora Pearl, "it was sex that sold".

Frances Wilson's attention to a single individual allows her to create an involving and substantial study; Katie Hickman vividly captures the magic-lantern quality of the courtesan's world. Both writers include lively details, and Hickman in particular knows how to put a footnote to entertaining use. There are some charming asides about such topics as mice-infested hairstyles, and one intriguing speculation. Lord Sandwich's famous snack might have been inspired by the courtesan Kitty Fisher, who was said once to have eaten a £100 bill between two slices of bread.

Sarah Bakewell's 'The Smart' is published by Vintage