Andrew Finkel’s The Adventure of the Second Wife is a beautifully crafted book, a boys’ own detective story that is also part history, part travelogue, part love letter to the city which has been the writer’s home for close on half a century.

The novel carries the subtitle The Strange Case of Sherlock Holmes and the Ottoman Sultan. Finkel explains in the acknowledgments that the inspiration for his tale was a single sentence in his friend Philip Mansel’s book Constantinople: City of the World’s Desire.

Here Mansel describes Sultan Abdülhamid II, the last Ottoman ruler, as a collection of contradictions: “subtle and silly, brave and frightened, cool and tolerant, modern and traditionalist, listening at one moment to the Koran, the next to the adventures of Sherlock Holmes, read to him at night from behind a screen in a specially commissioned translation.”

So a throwaway line in one book is made the central conceit in another. Holmes is still top billing, the detective who knows “nothing of your emotion but operates at the vertiginous level of reason”. But perhaps the portrait of Abdülhamid himself is the real ultimate piece of imaginative legerdemain. Finkel’s Sultan is a tragic figure who gives up his love of a Belgian girl to become Sultan – “forced to reject bourgeois monogamy for an Oriental harem”.

Has Abdülhamid ever been given a more sympathetic rendering? Of all the vignettes, I especially liked the story of how the Sultan narrowly avoided an assassination attempt. The carriage which was to take him to prayers outside the gates of the palace had pulled off without him. A shot was fired – the bullet lodging in the seat where Abdülhamid would have been sitting. This particular day he was late for the outing to the mosque. The reason? He was in his private chambers, buried in the latest Sherlock Holmes.

Finkel’s creation is Byzantine in the truest sense of that word: convoluted, involved, knotty, tangled, tortuous and complex, to cite just one dictionary definition. The plot twists take some following. But persist. The

Abdülhamid’s ignominious return to Istanbul was on The Loreley

A victoria carriage at Yildiz Palace, drawn by Turkoman mares journey is rewarding and Finkel is a master guide, his prose elegant, and often elegiac.

The Adventure of the Second Wife is set in Istanbul and London. Much of the action takes place in the Turkey of the 1890s and the London of Queen Victoria and Prime Minister William Gladstone. Other chapters depict the two cities a hundred years later, as Finkel’s characters set about trying to stand up the rumours that Sir Arthur Conan Doyle, creator of Sherlock Holmes, wrote an unpublished final tale commissioned by the Sultan, called ‘The Second Wife’.

This is the mystery at the heart of the novel. But the book is also a narrative of parallel but interconnected family histories. The narrator is a retired London doctor and Sherlock Holmes obsessive called John Watson. So he shares a surname with the fictional detective’s hapless sidekick. But we learn early on that he resides in Baker Street, where Holmes also once had digs.

In Finkel’s Sherlock Holmes redux, the Holmes figure is played by a woman, a fellow book sleuth, Leyla Arslan. She is a Turkish academic who shares many of the mercurial behavioural traits of the Victorian detective, not to mention some of his other more addictive habits.

The plot is hard to summarise, even without giving away the story. But much of the early chapters is taken up with describing the arcane world of Conan Doyle scholarship, peopled by that curious breed of literary anorak Finkel describes as Sherlockian scions who attend conferences and write papers on the four novels and 58 short stories that make up the Sherlock Holmes canon. Indeed it is at one of these academic gatherings that Watson and Leyla are said to have first met.

As the plot is propelled forward, becoming increasingly entangled on route, what becomes clear is that the main characters are also both on a journey of personal discovery.

In Watson’s case the great “reveal” is that his uncle Fred is none other than Rafiuddin Ahmad, a real-life figure in Queen Victoria’s inner circle, to whom Finkel gives a central role in the plot of The Adventure of the Second Wife and a part in the British Queen’s urgent diplomacy to restore relations with the Turkish Sultan and the Sublime Porte.

Leyla, too, is busy in the family archives, in her case working up an unfinished novel of a dead aunt, while also quizzing her elderly grandfather, who used to run the palace translation bureau, about the Sultan’s taste in literature. “His majesty had little sympathy for sentimental novels”, she is told. “He had a preference for stories that ended satisfactorily,” and particularly detective stories.

Like any good whodunnit, Finkel’s book is driven forward by unlikely coincidences, with the reader led up narrative culs-de-sac in pursuit of plot red herrings.

Finkel clearly knows his Ottoman history – his wife is the historian Caroline Finkel. And he deploys his final devices expertly, painting a colourful kaleidoscope of the dying days of the Ottoman Empire, the period of the Young Turks, when Abdülhamid is forced into exile in Thrace, Gallipoli, the brief British occupation of Istanbul, and finally the launch of the modern Republic.

Whether it is in the Topkapı, Yıldız or Beylerbeyi homes of the Sultan, Finkel cleverly interweaves known historical events with imagined goings-on behind the palace walls.

The real-life episodes include the earthquake of 1894, and the Sultan’s ignominious return at the onset of the First World War after being under house arrest in Thessaloniki, escorted back to Beylerbeyi aboard The Loreley, the German ambassador’s yacht.

As the story approaches its conclusion, Finkel even gives Sir Arthur Conan Doyle a walk-on part, depicting him travelling to Istanbul on his honeymoon with Jean, his second wife. Yes, everyone in this novel seems to have a second wife. Of course, in Muslim Turkey this is nothing exceptional.

Finally, what keeps the novel ticking over is the quality of Finkel’s writing, whether the joshing dialogue between Watson and Leyla or his meditations on culture, class and cooking. Cornucopia readers will know that Finkel is a fine restaurant critic, and his novel is also full of wonderful descriptions of food.