My introduction to alternative history was Philip K.Dick’s The Man in the High Castle, which I read when I was about 20. I hesitate to call it my favourite, though.That prize goes to Len Deighton’s SS-GB, which combines an interesting alternative timeline where the Nazi invasion of Britain takes place with a detective/espionage thriller. Since Len Deighton has also written some pretty good popular historical books on related subjects (e.g., Fighter and Blitzkrieg), I took his ideas as being fairly accurate.
And now here comes Derek Robinson, whose books I also enjoy, who enjoys getting to the heart of matters – at least as he sees them – which he has done in novels such as A Piece of Cake and Damned Good Show, in which he explores the myths that have grown up around the historical episodes he is writing about. So Invasion 1940 is there to prove to the reader that the Battle of Britain, though important, had very little to do with stopping Operation Sealion (the planned Nazi invasion of Britain).