Decadent luxury, steamy sex and a strong whiff of sordid imperialism - try a Roman blockbuster, says Mary Beard
Dinner with the Roman emperor was a risky business. Poisoned mushrooms were a renowned menu item; people literally keeled over and died. The Roman historian Tacitus gives a memorable account of one such occasion: an evening hosted by the young monster Nero in the late 50s AD, from which his little stepbrother (and rival) Britannicus was carried feet first. It was the usual trick (poison in the water used to cool the wine - which the taster forgot to taste) and, as Tacitus points out, the usual dilemma for the dinner guests. Should they just take no notice and carry on tucking into the stuffed dormice as if nothing had happened? Or should they play really dumb and call a doctor for the poor boy? When a paranoid emperor was around, there was no safe course.

Lindsey Davis revisits this scene in The Course of Honour, her recent novel now issued in paperback (Arrow, pounds 5.99). Taking a temporary break from her famous series of Falco mysteries (Marcus Didius Falco, the Roman sleuth... ), she tells the story of ex-slave Antonia Caenis and her long-term lover Vespasian, the back-to-basics emperor who, after a very nasty civil war, followed Nero on to the throne. (He was the one who supposedly joked on his deathbed, "Goodness me, I think I'm becoming a god" - so pointing the finger at the super-human ambitions of his predecessors.)

There are some uncomfortably sentimental sides to Davis's new tale, as well as some (would-be) steamy bits of sex that Falco and his partner Helena would never have stooped to. But Caenis herself is cleverly drawn, as a spirited, original, strikingly down-to-earth observer of a corrupt and corrupting world; and her whole story, from the moment she picks up the gauche young Flavius Vespasianus in a back pantry of the imperial palace to her final instatement more than 40 years later as official imperial mistress, is as hard to put down as any of Davis' novels - whether or not you know anything of the historical background.

For those who do know something of the historical sources on which she draws, it is even more fun. Davis smartly makes Caenis one of the guests at Nero's deathly dinner party (as minder of the doomed Britannicus, in fact); and proceeds to subvert Tacitus' account through Caenis' eyes. The food was actually ghastly, overblown and overcooked official catering. And the murderous draft of poisoned water didn't stop with its intended victim. Cups are shared at a party, poisoned water gets around, and before long Britannicus' friend Titus (Vespasian's son) was very ill indeed...

As always, Davis is brilliant at conscripting famous stories of classical literature into her own tale, and at the same time turning them upside down. It's no wonder that she's the professional classicists' own favourite (and is currently president of the national Classical Association).

But Lindsey Davis is just the tip of an iceberg. Novels about ancient Rome appear at the rate of something like 20 a year in this country alone; and since the Fifties they have outnumbered novels set in ancient Greece by more than three to one. Why are they so popular? And why, in a world that places itself so firmly in the Hellenic tradition, is it sordid imperialist Rome rather than gleaming democratic Athens that catches the novelistic imagination?

Part of the answer is, presumably, precisely that: the fact that ancient Rome was so sordid. The Roman empire was a heady mixture of autocracy (in the shape of mad or bad emperors), decadent luxury, imperialist oppression (conquered territory from Britain to the Sahara) and violent religious revolution (the extraordinary triumph of Christianity over a lot of other equally plausible alternatives); and as such, it makes a great background for debating the "human condition" (or our late 20th-century version of it, at any rate). That certainly is what you would conclude from other pieces of a clutch of recent Roman fiction.

The most high-mindedly intellectual of these is Mario de Carvalho's prize- winning A God Strolling in the Cool of the Evening (Weidenfeld & Nicolson, pounds 16.99, translated from the Portuguese by Gregory Rabassa). Roman stories are not just a British phenomenon. Set in an outpost of empire (Portugal) and a century later than Lindsey Davis's novel, in the reign of the philosopher- emperor Marcus Aurelius, this is a lyrical meditation on the idea of ageing and of history itself (predictably, the preface asserts "This is not an historical novel"). Its narrator, Lucius Valerius Quincius, is the chief magistrate of an imaginary Roman town in Iberia: a man who lives in a culture of equally imaginary classicism. It is a culture where friends swap antiquarian books, and funeral speeches regurgitate the bons mots of a golden age 200 years earlier, while all the time, in real life, the barbarians are literally at the gates. Here, in this strange mixture of nostalgia and military Realpolitik, Lucius meets Christianity in the shape of one particular Christian woman, Junia.

This is, of course, the oldest theme in the Roman book (and movie). A whole string of moralising stories early this century featured a hunky young pagan soldier or senator (often assigned to anti-Christian duties by a viciously depraved emperor) and a gorgeous (but pure) Christian girl. Soldier falls for girl, converts to Christianity and ends up with her in the final chapter (or scene), bravely facing the lions in the arena; no sex but a noble martyrdom to be proud of and to finish the story. So, in outline, Sign of the Cross, Quo Vadis and a whole host of improving works that once brought the Romans into the average sitting-room and Sunday school.

A God Strolling is a clever fin de siecle reworking of that simple narrative. There is no climactic martyrdom for anybody, but a series of questions - not only about the nature of Christianity itself, but also about political responsibility: is it, or is it not, Lucius' duty to bring Junia to trial? Is he free of her blood on his hands, if he passes the buck for her execution to the central authorities in Rome?

Allan Massie's Roman stories also have an ostensibly political agenda; elegantly written, but rather more predictable explorations (against a Roman background) of the nature of ambition and obsession, and of the vulnerability of the autocrat. His much admired "Roman Quartet" - Augustus, Tiberius, Caesar and now Antony (Sceptre, pounds 16.99) - takes us to the most familiar period of Roman history of all (from Shakespeare, if nowhere else): the dictatorship and assassination of Julius Caesar, the civil wars that followed with Antony and Cleopatra, and the carefully hedged autocracy that emerged under the first Roman emperor Augustus. Antony is cast in the form of Mark Antony's memoirs, dictated to his secretary just before his final defeat. It is written quite explicitly as a counterpoint to Massie's earlier Augustus, covering the same ground.

Seen together, these very different versions of the rights and wrongs of the civil wars (plus the sharp editorial comments of the secretary, whose voice eventually takes over to tell the very end of the story), offer a challenge to "straight" history. They force the reader to see that there is no single story to civil war - only a series of irreconcilable versions and incompatible self-justifications. This is a clever use of fiction to make an important historical point.

It's a point that would be quite lost on Colleen McCullough - author of The Thornbirds and now, with Caesar, (Century, pounds 17.99) on the fifth and final novel in her "Masters of Rome" series (slightly shorter than some of the others, at a modest 664 pages). A horrible combination of self-confident narration, pseudo- accuracy (half a dozen maps, a 40-page glossary and an essay on sources) and some of the worst dialogue ever written in the history of the English (or Latin) language, it does at least remind us of what the other more tastefully intellectual books might have us forget. Rome really was a city built on epic proportions. A vast and vulgar blockbuster, Rome's story has always asked to be told big.