What if Hitler had had a son of his own, though did not want to acknowledge the fact, and asked another couple to bring up the child as their own? Hitler's personal agenda would be paramount, of course, and so the fate of the child would depend on the whim of the dictator.

It is giving away no secrets to say that this is the thrust of Siegfried by the Dutch writer Harry Mulisch (Penguin, £16.99), and an extraordinarily well told tale it is.

The book concerns a famous author, Rudolf Herter. During the course of a television interview, he is asked whether a work of imagination can help us to understand the nature of evil; whether a modern-day author can, in fact, write about the horrors or war and of Adolf Hitler in particular. This question sets Herter's mind whirring; even more so when he is invited by an elderly couple to their flat, and they confide in him -- in the strictest confidence -- their fascinating, tragic secret.

The book is not merely the telling of the secret, however. The reader is brought into Herter's mind, and his thoughts on truth, imagination and memory. It is as disturbing and haunting to the reader as to the author within its pages.