A list-serve I follow recently ran a list of recommendations by history professors of the best one-volume histories of WWII. I though it might interest some of our readers:
Gerhard L. Weinberg, A World at Arms: A Global History of World War II (10 recommendations)
Williamson Murray and Allen Millett, A War to be Won (5 recommendations)
Richard Overy, Why the Allies Won (4 recommendations)
H.P. Willmott, The Great Crusade: A New Complete History of the Second World War (3 recommendations)
Several posts mentioned that, while Weinberg's book is the best one-volume history of the War, its length (and expense) might make it a little daunting for undergraduates, and several suggested that Williamson and Murray or Overy might be more accessible. Williamson and Murray were also noted as offering a more operational account.
Ronald Spector, Eagle Against the Sun received four recommendations as a history of the Pacific War.
Also recommended were: Miller, Donald A., The Story of World War II- Revised, expanded, and updated from the original text by Henry Steele Commager; John Costello, The Pacific War, 1941–1945; Russell Weigley, Eisenhower's Lieutenants; Norman Davies, No Simple Victory; John Toland, The Rising Sun; Evan Mawdsley, World War II: A New History.