I recommend "Magic : The Untold Story of U.S. Intelligence and the Evacuation of Japanese Residents from the West Coast during WW II," by David D. Lowman, which details the intelligence about Japanese and (alas!) Japanese-American plans for espionage and sabotage in the United States at the outset of WW II, and how that intelligence led to the internment order.
Of course, there were many Japanese-Americans who distinguished themselves---indeed gave their lives---in both the European and Pacific theaters for their country in WW II. Their language and cultural skills were particularly valuable in the Pacific theater, and the heroism of the J-A "Go For Broke" brigade fighting in Europe is legendary. Nonetheless, there was more than one disloyal "bad apple" among Japanese-Americans at the time, and we have to face that fact in our history if we're going to be honest. We can't allow pious Politically Correct revisionism to prevent us from dealing appropriately with individuals allied with our enemies because of ethnicity during time of war.