World War I & World War II The Rest of the Story
Amazon.com: World War I: The Rest of the Story and How It Affects You Today, 1870 to 1935 (Uncle Eric Book): Rick J. Maybury,Jane A. Williams: Books Amazon.com: World War II: The Rest of the Story and How It Affects You Today, 1930 to September 11, 2001 (Uncle Eric Book): Rick Maybury,Jane A. Williams: Books
I finished the first one in a few hours I couldn't put it down. Been working through the second one slowly. It's an "Uncle Eric" book which is written as a series of letters to Eric's (Rick Maybury) fictional nephew so it's simple and easy to understand yet very engaging.
Essentially, it covers the economics of the wars and shows how they were nothing new in the history of Europe and why the U.S. Didn't need to get involved.