Personally, all that I new about J. Robert Oppenheimer was his time during Project Manhattan and a few details about his show trial in 1954. This book managed to bring a lot more context to these events and show me as close it is possible the real Oppenheimer.

What else can I say, this is probably the best biography of J. Robert Oppenheimer there is and together with Richard Rhodes' Making of the Atomic Bomb and Dark Sun makes the penultimate atomic trilogy.