For children’s books, Devils Arithmetic by Jane Yolen. About a modern girl who doesn’t understand at all what her grandparents went through in the camps during WWII finds herself in Poland in 1942. The plot is a little contrived, but I remember it was the first books that made me cry. My Antonia by Willa Cather was the second.
Sharon Creech’s Walk Two Moons is not only extremely sad…it’s well written. How often do you see intricate subplots in children’s literature. And, if you’re not paying extremely close attention, the end is quite a surprise.