Third Reich Victorious: Alternate Decisions of World War II by Peter G. Tsouras
This collection of alternate history scenarios looks at what would have happened if, for example, the Germans had captured the whole of the BEF at Dunkirk, the RAF had been defeated in the Battle of Britain, or if Rommel had been triumphant - in short, how the Germans could have won the war, and what the consequences would have been.