The Book of Lights — Chaim Potok

Gershon Loran, a quiet rabinical student, is troubled by the dark reality around him. He sees hope in the study of Kabbalah, the Jewish book of mysticism and visions, truth and light. But to Gershon's friend, Arthur, light means something else, the Atom bomb, his father helped create. Both men seek different a refuge in a foreign place, hoping for the same thing....