When the Scottish writer Sir Walter Scott invented the modern historical novel in 1814, he knew what he was doing. In Waverley, which is set in the Jacobite uprising in Scotland of 1745, Scott applied to the crude manners and political antagonisms of 70 years earlier the moral insight and sentimental refinement of the Scotland of his own age. The result was unhistorical, but, in the rage for Waverley and its successors, from A Tale of Two Cities to War and Peace, who cared?

Writers of genre fiction also took to history to give novelty and prestige to literary formulas. Who has not read a police procedural at the court of Charlemagne or an erotic thriller set in Minoan Crete? Benjamin Weaver, the hero of A Spectacle of Corruption, soon turns out to be the hard-outside, soft-inside private investigator of the noir thrillers inserted into 1720s London: Philip Marlowe done up in a wig and buckles.

A Jewish ex-prizefighter turned professional "thieftaker," Weaver appeared in Liss's first novel, A Conspiracy of Paper. Liss took as his model Jonathan Wild, a Georgian gangster who worked both sides of the law until his execution in 1725, but gave him a modern mind and heart among the dead dogs and banknotes. In his next book, The Coffee Trader, Liss invented a great-uncle for Weaver among Sephardic merchants in the Amsterdam of the 1650s. He now returns to both Weaver and 1720s London.

The story unfolds during the election of 1722 in London's Westminster where, unusually for 18th-century England, the franchise was democratic. Amid the intrigues of Whigs and Tories, Hanoverians and Jacobites, the bribes and political violence, Weaver finds himself implicated for a murder he did not commit. All sorts of terrific things happen. Weaver is tried before an outrageously partisan judge, escapes from Newgate prison, holds an informer's head in a chamber pot, finds the love of his life turned Christian and married to a Tory politician, takes part in election riots. Yet few will prefer Spectacle to novels one and two.

The chief problem is that Liss is much less interested in ancient politics than in the revolutions in finance and commerce that formed the historical backdrops to the first two novels. Nothing dates like party antagonism, and to say that Liss doesn't really understand the primordial cleavage in English politics between Whig and Tory is no insult: Only a handful of today's Britishers do. As Jew and outsider, Weaver has the privilege of asking elementary political questions that Liss takes little trouble in answering.

Liss compensates not with his strengths, which are in character, especially women, and action, but as Raymond Chandler does, with yet another twist of plot. The unraveling of the plot requires a lot of talk, usually just one character to another. Many novelists can't write dialogue for more than two characters at a time, but Liss can, and it is a mystery why he doesn't.

The elaborate plot also requires acres of back story, which is not recommended in a book where the main narrative is already in the distant past. At one point, Weaver blurts out: "So the Tories kill him, and make it look like the Whigs killed him in an effort to harm the Tories. That is a mighty deep game." Not deep at all. Those are sentences of a kind every novelist knows and fears, and they mean: Your plot is out of your control. You must start again.

Even his London has lost some of its oddity. Liss has abandoned his Jewish milieux, and the beautiful Miriam has become the beautiful Mary. The social décor tends to the commonplace or anachronistic. Gin, tobacco smoking, labor combinations, prize fighting and cricket bats became widespread a generation or even two generations posterior to Weaver's story. Liss also uses words that originated long after the 18th century was over: echelon, perambulator, upcoming, attendee, visit with, communist, semantics. The effect is to break the spell of the book, like a stage actor dropping out of character. The question is whether Liss has settled into a sort of Weaver franchise, in which plots become more complex, action more brutal, language and morals less authentic and characters more simple, or whether he sets off again in search of the only thing a novel cannot do without, which is novelty.