Ian Caldwell and Dustin Thomason: The Rule of Four

Literature that claims to unlock codes, ciphers and hidden secrets is enjoying a vogue. Roland Barthes identified this as one of his modern "Mythologies": the belief that the universe is a kind of safe which humanity could open if we could only find the combination.

The Hypnerotomachia, or "The Strife of Love in a Dream", seems to Ian Caldwell and Dustin Thomason to be such a key. It is one of the principal texts of Renaissance culture, consisting of erotic reveries and arcane discourses on subjects such as sex, architecture, gardening, music, pyramids and nymphs.

Published in a superbly illustrated Aldine folio in 1499, the Hypnerotomachia was one of the most beautiful books ever to leave a press. Most scholars believe it was collected from classical and possibly Arabic sources by Francesco Colonna, a sophisticated Venetian priest who lived to the age of 94.

The Rule of Four is a thriller based on the symbols and fantasies of the Hypnerotomachia. This fiction purports to unlock a great secret of the past, which brings a deadly pursuit to the students who have discovered it. Caldwell and Thomason have turned Colonna into a Roman nobleman to suit their purpose, which involves a mysterious cargo of immense value arriving in Genoa. Its subsequent history is unravelled by working out ciphers in the text.

I hate to spoil the fun by pointing out that the original, far from being the unattainable mystery the authors claim, was published by Thames & Hudson in an excellent version by Joscelyn Godwin in 1999. So their assertion that there has been no English translation since the 16th century is quite misleading.

Still, as they say, "A riddle is a castle built on air", and the plot keeps bubbling along. This is a group-of-students mystery, of the Donna Tartt kind. Clever Paul is doing a thesis on the Hypnerotomachia, handsome black Charlie is a medic, Gil a rich sophisticate and Tom, the narrator, the son of an academic who became obsessed with Colonna's story. They discover an old diary and their decipherment of its secrets, they claim, results in death and danger.

The four are studying at Princeton, where the student society has rituals as impenetrable as anything in the Hypnerotomachia. There is much oak-panelling and running round with no trousers. The bitcheries of academic life are immaculately observed, in a fascinating glimpse into a secretive modern world: that of the American overclass.

As a thriller, The Rule of Four is not especially fast-paced, but the personalities and relationships are well-handled, as is the narrator's conflict between his desire for a normal relationship with his girlfriend and the sense that he is being dragged into dangerous obsession. This is good entertainment, a Da Vinci Code for people with brains. But the authors must know about Godwin's translation and should acknowledge it, even if only in a postscript.