Fleming, Peter. Operation Sea Lion: The Projected Invasion of England in 1940, An Account of the German Preparations and the British Countermeasures [vt Invasion 1940: An Account of the German Preparations and the British Countermeasures]
Divergence: 1940 CE
What if: Germany occupied England in 1940 or made no invasion preparations at all.
Comments: Mostly background material but chapter 20 discusses events which could not have occurred if either supposition were true.
Published: As Operation Sea Lion, Simon & Schuster 1957, Ace [[date unknown]], Greenwood 1977 (0837194296).
— As Invasion 1940, Hart-Davis 1957, Pan 1975.