Alternative history in the guise of a view (through palls of smoke) of Britain under partial Nazi control might be a sound basis for a thriller; but add a little tinkering with time's arrow through the medium of dreams and you've leapt to the loopier end of the science fiction spectrum.

In Stephen Baxter's new take on an established story – the Battle of Britain and its consequences – the reader is introduced to the inter-war work of British aeronautics engineer John William Dunne who evolved the idea that past, present and future are simultaneous and differ only in our perceptions of them. After contemplating precognition he suggested that in dreams the mind could perceive both past and future. His ideas attracted the attention of Aldous Huxley, J.B. Priestley and H.G. Wells, and in Baxter's novel, they excite the attention of a group of typically obnoxious Nazis who believe that a little tinkering with the past via dreams will enable them to (among other things) defeat the United States without firing a shot.

The story's preliminary architecture is established when the Nazi forces inflict a partial defeat on the British, cross the Channel, make a lodgement in the south-east of England and drive north. The British government moves to Yorkshire and the combatants fight each other to a standstill just south of London.

Enter Ben Kamen, a gifted young physics researcher who evaded the clutches of the Nazis while working on dream time travel in Cambridge, Massachusetts, who now wears the uniform of the British Army and is a prisoner of the Germans. The Nazis are bent on harnessing his knowledge to their own ends. The British are typically slower to grasp the peril that confronts them but finally assemble a counter-force led by a commando and an American journalist.

So proceeds the fourth book in Baxter's Time's Tapestry series. The pace is brisk, the narrative low-key, the action continuous and the characters an entertainingly sketched mix of the bumbling and the dastardly. The Nazis are revolting, the British largely modest and bumbling but helped through the darkness of war by beacons of courage and wisdom such as Mary Wooler who manages to find her way to the right place at the right time without the help of dreams.