It's one of the most successful - and surprising -- of phenomena in the entire crime fiction genre: detectives (and proto-detectives) solving crimes in earlier eras. There is now an army of historical sleuths operating from the mean streets of ancient Rome to the Cold War era of the 1950s. Barry Forshaw, has written a lively, wide-ranging and immensely informed history of the genre, which might be said to have begun in earnest with Ellis Peters¿ crime-solving monk Brother Cadfael, but which has now taken readers to virtually every era and locale in the past.