
This is the subject Ds#1 wanted to study this year. With
Memoir '44 being his favorite board game it was hardly a surprise. Between what I already had and the recommendations in
For the Love of Literature
by Maureen Wittmann (which I now have on my Kindle), I was able to easily put a unit together.
For spines I have several books.
World War II for Kids: A History with 21 Activities
by Richard Panchyk; and
America: The Last Best Hope (Volume II)
by William J. Bennett. (I see that a Volume III is coming out next month covering 1988 to 2008.) I also have a couple of OOP books for younger kids:
The First Book of World War II by Louis L. Snyder and
America Moves Forward by Gerald W. Johnson.

The Landmark Book series has a lot of titles on the subjects.
I own eleven of them, plenty to keep my kids reading. If you are not familiar with this series, they are non-fiction books told in a story format. They have too much fact to be historical fiction yet the details in the dialogs, for example, are made up. I suppose you can consider them on the factual end of historical fiction.
Bethlehem books has quite a few WWII historical fiction titles that my boys are enjoying, like
Penny for a Hundred for Ds#3, T
he Secret War of Sergent Donkey for Ds#2, and
Enemy Brothers for Ds#1. We own
these.

Some of Maureen's recommendations include
Twenty and Ten
by Claire Hutchet Bishop. We were able to borrow
Miracle at Moreaux
, the film based on it. She also listed
Against the Day
an out of print book by Michael Cronin that turns out to be the first in a series of three that can still be gotten cheaply through used book sellers. We're waiting for them to arrive. She recommends some great picture books that I got from the library like
The Snow Goose and
The Secret Seder.

I purchased
Saint Maximilian Kolbe: Mary's Knight
by Patricia E. Jablonski and
Saint Edith Stein: Blessed by the Cross
by Mary Lea Hill, both in the
Encounter the Saints series. I even found a 1959 biography of Pope Pius XII by Richard Cushing in the juvenile section of a local library, though it was also in a college collection. At 180 pages maybe Ds#1 could read it, but I'll have to read through it first.
I've put my husband on the task of recommending some classic WWII movies--John Wayne comes to mind but I am sure there's many more. So far Ds#1 is reading the historical fiction faster than I can get them in, and that's a good predicament to be in.