This book is collection of letters by J. Robert Oppenheimer, physicist and director of the Manhattan Project, written between the years 1922 and 1945. The letters are divided into five sections chronologically: letters written during Oppenheimer’s days as a student at Harvard University, his post-graduate study and early career in Europe and America, his work at Berkeley, his first years as director of the Manhattan Project, and his final months on the Manhattan Project, when the first atomic bomb was created and tested. Many of the letters deal with areas of physics, such as quantum field theory, cosmic rays, and nuclear physics, but the letters also display Oppenheimer’s knowledge of literature, history, and philosophy, as well as reveal interesting aspects of his character. A few particularly insightful letters written by others addressed to Oppenheimer have also been included. The book contains some photographs, a brief chronology of Oppenheimer’s life, and a listing of his scientific papers. The introduction and commentary throughout the book include biographical information to give the letters context.