The Snake Stone, by Jason Goodwin

This is the second book in Jason Goodwin's deeply original series set in 19th-century Istanbul with a detective who happens to be a eunuch. This detail set off a prurient train of thought. A castrated Sherlock Holmes would not have made much difference, since Holmes was uninterested in sex. Philip Marlow: unthinkable; Michael Dibdin's Aurelio Zen might even have welcomed the state, so engrossed was he in metaphysics.

The operation has certainly focused the intellectual powers of Yashim, Goodwin's subtle, de-orchidated sleuth, who winds a scary path through the ancient pitfalls of Istanbul. The beginning is an enticing puzzle: a poor French archaeologist appears to have possessed an arcane 16th-century text full of clues leading to a secret treasure of Byzantium, hidden away at the moment of the Ottoman invasion. The theme was identified by Roland Barthes in his essay "The Brain of Einstein": there is a great secret that supreme intelligence can unlock. It's always a delight for bookish readers, and its appearance here is handled with great skill, leading to the discovery of a secret society among the literati of the Golden Horn.

When the archaeologist is murdered, the sultana Validé, Yashim's patroness and herself French in origin, aids him in his quest, which has many dangerous twists down through layers of the history of the wicked old city. The clues from antiquities are many and cryptic: obelisks, snake-headed columns, underground cisterns, all signifiers of past corruption and tragedy.

Dr Millingen, the medic who finished off Byron with enthusiastic bleeding at Missolonghi, pops up in Istanbul as the sultan's physician, with a splendid collection of louche characters. Yashim may be "unseminar'd", but he is still appreciative of beauty, especially that of the archaeologist's lovely young widow. She plays a leading part in the unwinding of a plot that maintains tension along with its rich cargo of exotic detail.

The Snake Stone compares with The Name of the Rose in its sense of historical reference through layers of meaning. It bears multiple re-readings, especially the bravura account of the spice bazaar. The accounts of food preparation are delicious: Yashim's meze, prepared according to recipes from the sultan's kitchens, with crisped mackerel skins, nuts, tiny aubergines, white cheese and courgette flowers, made me drool. Have a napkin handy when reading this book.

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