This is an historical novel about Afghanistan (though not a traditional historical novel since, among other departures from tradition, what seems like a romantic thread comes to a climax, produces an illegal child, but doesn't end happily or even decisively). Another departure is that the writer is British but his title character is not Alexander Burnes, the Englishman, but Dost Mohammed Khan, the Afghan.
Most of the characters are real, including both Burnes and Dost Mohammed, and there's a list of books he consulted in writing it, including Peter Hopkirk's The Great Game
, one of my favorite nonfiction reads of the last 10 years.
The sympathy is not with the British in the First Afghan War--where the British were soundly defeated and mostly all killed--but with the Afghans who were extraordinarily violent. It's a very 21st century view of a 19th century war, though at the time there were participants who recognized British treachery in driving out Dost Mohammed Khan in favor of a decadent ex-emperor whom the Indian Governor thought might protect Britain from a Russian invasion of India. In the beginning of the novel, we see Alexander Burnes as the toast of London for having been the first Englishman received in Kabul, but the social events at which he's feted read very much like social events in later Dickens novels--the focus is on the hollowness of both the characters involved and the events and the social amenities they practice. Amazing that's done without detracting from the complexity and humanity of the main characters who attend the events.
While the novel is more or less chronological, it doesn't feel like it while reading since Hensher jumps from one character and locale to another and seems to focus on parochial and local events rather than on a step in the historical timeline. You may not even recognize at first that the novel is historical, especially if you do not know about the first Afghan war. On the other hand, you'll not miss Hensher's reimagining of the British Empire. An author who can both make local characters and events real AND convey an overarching evaluation--and criticism--of a past era is an author to take seriously.
This is a serious novelist, imitating familiar novelistic techniques in a new context, engaging ideas both historical and artistic. He warns us in the Afterward not to expect historical exactness, that even the characters of some historical figures are changed. I found it impressive as a novel and thought provoking as a view of history.
I should say that I found this novel in AS Byatt's answer to an interviewer's question about who she reading among younger writers. And there's a sentence in the "Errors and Obligations" section at the end acknowledging her advice. The book also has a glossary, though most of the terms used are clear in the context or actually defined in the text--and a cast of characters. One imagines an editor suggesting the latter for a book which involves so very many characters, but this cast is at the end--where you may not see it until you're nearly finished. And the characters are only named, not described or put in any context.