Michelle Malkin wrote an excellent book on the same subject, 'A Case for Internment', that presented angles that I had not heard previously. Perhaps similar to what was written in 'Magic'.
Trying to play 'Monday Morning' quarterback, from the comfort of American society some 40 - 50+ years after the war, and asking why those who just had their Pacific Fleet basically destroyed in one day (and the fall of the Philippines, shortly afterward) could have acted the way that they did - is the epitome of moronic arrogance.
MAGIC is very interesting in that it includes reproductions of many original letters, intel items, etc, in the book. It contains its own footnotes on many items, as it were.
It wouldn’t surprise me if it were a main source for Malkin’s book.