First WW2 book I read was probably Hitler 1935-1945 nemesis by Ian Kershaw I believe. It took awhile but was very informative and very interesting.
I was a very literate youth. I believe the first book on the WW2 topic I ever read was a novelization of the Combat tv series that my mother had, she was a fan of that show as a kid. Also, when I read Shirer's "Rise and Fall of the Third Reich" when I was nine years old it scared the hell out of me.
The first one I can remember having read was a historical fiction called "Radar Commandos." It was a fictionalized account where a young French boy is recruited (having escaped to England) to help commandos raid the radar station at Bruneval France.
Now that I remember the first I 'read' was a giant book called "Great Naval Battles of History" which contained nearly 300 big full-page paintings of the battles all the way to Jutland... An uncle gave it to me when I was 4...
Do Commandos comics count? I think the first WW2 book I looked at was probably my dads book, 'Fighters and Bombers of WW2' (Bill Gunston I think) which I flicked through frequently before school, managing to learn to ID almost anything in it.
IIRC, it was an illustrated paperback book called "The History of Tanks" (German tite: Die geschichte der Panzerkampfwagen) by Kenneth Macksey and John Batchelor. First I was fascinated to find the pictture of my toy tank (Tiger 1) in the book, later I re-painted the blueprints in it, again later I read the text and learnt all the technical specifics advantages/disadvantages described there. So something went wrong and I became a WW II-nerd. I still have the book, awfully tattered, but I can't throw it away. First book on East front was "Paul Carell"'s popular BARABROSSA, it took literally years to heal the harm of disinformation and bias this book done to me. Cheers,