There's a fascinating sub-genre of science fiction known as alternate history. The idea is that at some point in the past, history diverged from reality, resulting in a different present. Perhaps the most acclaimed of these books is Kingsley Amis's The Alteration , set in a modern England where there had not been a reformation - but James Alistair Henry arguably does even better by giving us a present where Britain is a third world country, still divided between Celts in the west and Saxons in the East. Neither the Normans nor Christianity have any significant impact. In itself this is a clever idea, but what makes it absolutely excellent is mixing in a police procedural murder mystery, where the investigation is being undertaken by a Celtic DI, Drustan, who has to work in London alongside Aedith, a Saxon reeve of equivalent rank, who also happens to be daughter of the Earl of Mercia. While you could argue about a few historical aspects, it's effectively done and has a plot...