Prague Fatale, By Philip Kerr

How many lives can Bernie Gunther have? The dogged Berlin policeman of Philip Kerr is now enjoying – if that's the word – his eighth. The Gunther books appear out of chronological sequence, but the protagonist remains consistent, stoical, appalled by others and himself, carrying the darkly flaming torch of gallows humour. After South America, Cuba and the US in the 1950s, he's back in the Second World War, this time in the service of the monster Reinhard Heydrich, Reichsprotector of Bohemia. It is September 1941.

Gunther would rather investigate proper murders in Berlin, but he is summoned to Prague to a house party of high-ranking Nazis at Heydrich's rural residence (a castle, naturally) to act as his bodyguard. The Reichsprotector's concerns, apart from his feud with Himmler, include the Czech resistance and the presence of a spy in the SS. But Gunther is diverted into investigating the killing of one of Heydrich's adjutants.

This is a locked-room murder, worthy of Agatha Christie, whose novels Heydrich seems to enjoy in the intervals of his super-human schedule. We glimpse his crowded diary, including an appointment in Wannsee. That tactfully positioned moment of horror rather outdoes the overcrowded population of the castle: like Christie characters, the Nazis tend to blend into one other.

The plot is skilfully contrived, with a trapdoor built into the form, but less interesting than Gunther's observations. He struggles to preserve something of himself from the moral destruction in which he has already been obliged to participate while serving in a police execution unit on the Eastern Front. Now he finds a distorting mirror in the wry pragmatism of his assistant, Kahlo, who describes himself as "a steak", brown on the outside but red in the middle.

Kahlo needs promotion to afford a family. Gunther's wife, though, is long dead, killed by the 1919 influenza epidemic, and he knows there is no future in his affair with the beautiful bar girl Arianne. The truth of this is laid out in horrifying and perhaps gratuitous detail when Gunther learns the real facts of the case – a reminder, perhaps, that Nazism is rather more than a sinister form of entertainment. If so, Kerr may be asking too much of his chosen form.

Nevertheless, Prague Fatale remains as absorbing as its companions in the series. Unlike some writers of historical thrillers, Kerr is able to let period detail live its own life. The early passages, where Gunther investigates the killing of a foreign worker on a Berlin S-Bahn station, are particularly effective: the blacked-out city is hospitable to murder, food is short and it is reported that the tapir in the city zoo has been stolen and eaten. On the radio, Hitler and Goebbels instruct the nation to give to Winter Relief. The Wehrmacht has reached Kiev, and nothing can go wrong, surely. Kerr depicts this deranged normality with unfussy authority.

Sean O'Brien's 'November' (Picador) is shortlisted for the T S Eliot Prize