2 books · Ages 10–14 · Chapter Books
Witness to History is a 2-book series for ages 10–14 by Clive Lawton. Each book stands alone — start anywhere.
Start anywhere — each book stands alone.
That said, Hiroshima: The Story of the First Atom Bomb and Auschwitz: The Story of a Nazi Death Camp are great first picks.
No particular order needed — browse and pick what catches your eye.