Hypothetical history is alluring stuff, geared to bring out the best in historians and writers of speculative fiction alike. What if Napoleon had taken Moscow? What if the South had won the Civil War? Longmate has produced an exciting scenario to show what might have been had Britain succumbed to German invaders. He begins with an examination of Operation Sea Lion and British steps to cope with such an invasion; then switches deftly to fiction to show what happens when the RAF fails to repel the Luftwaffe, German forces establish a beachhead in Surrey and Kent, and the indomitable Churchill dies with revolver in hand as the Wehrmacht overruns London. It's a shade melodramatic, no doubt reflecting the book's origin as a BBC series, but it functions nicely as a bridge into the main part of the book -- an examination of what life would have been like in Nazi-occupied Britain. The material is both ""realistic"" and imaginative, the scope considerable, and the author's-conclusions logically unassailable.