Ivan Jablonka's grandparents' lives ended long before his began: although Mat s and Idesa Jablonka were his family, they were perfect strangers. When he set out to uncover their story, Jablonka had little to work with. Neither of them was the least bit famous, and they left little behind except their two orphaned children, a handful of letters, and a passport. Persecuted as communists in Poland, as refugees in France, and then as Jews under the...