Hi Tim !
You can read more about the importance of RADAR here:
http://en.wikipedia.org/wiki/Tizard_Mission
"When the members of the Tizard Mission brought one (radar magnetron) to America in 1940, they carried the most valuable cargo ever brought to our shores."
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Although it's a completely different subject (WW2 development of the atomic bomb as an combined effort of the british/americans) the following book is one of the most interesting an well written books I have ever read, and beside that it's also an almost full history of WW2:
Richard Rhodes: The Making of the Atomic Bomb; 13.60 US$ very well invested ;-)
http://www.amazon.com/Making-Atomic-...2646688&sr=1-1