Michael Gordin, Five Days in August: How World War II Became a Nuclear War (2007), chapters 1, 2, 7.
Compare the photographs of Hiroshima, Nagasaki, and Tokyo in "War's ending," LIFE magazine (20 August 1945).
Henry De Wolf Smyth, Atomic Energy for Military Purposes (1945).
Kenneth T. Bainbridge, Trinity (1945).
Gar Alperovitz et al., The Decision to Use the Atomic Bomb and the Architecture of an American Myth (1995).
Spencer Weart, "The news from Hiroshima," Nuclear Fear (1988), chapter 6.
J. Samuel Walker, Prompt and Utter Destruction: Truman and the Use of Atomic Bombs Against Japan, rev. ed. (2009).
Wilson D. Miscamble, From Roosevelt to Truman: Potsdam, Hiroshima, and the Cold War (2007).
Tsuyoshi Hasegawa, Racing the Enemy: Stalin, Truman, and the Surrender of Japan (2004).
Wand Wilson, "The winning weapon? Rethinking nuclear weapons in light of Hiroshima," International Security 31 (2007).
Barton J. Bernstein, "The atomic bombings reconsidered," Foreign Affairs 74 (1995): 1-27.
Barton J. Bernstein, "Truman and the A-Bomb: Targeting Noncombatants, Using the Bomb, and His Defending the "Decision"," Journal of Military History 62 (1998): 547-570.
Murray Sayle, "Did the Bomb end the war?" The New Yorker (1995).
Michael D. Gordin, "The embrace of atomic bomb orthodoxy and revisionism," Reviews in American History 40 (2012): 500-515.
You can watch a debate on Truman's decision to use the atomic bomb (2014).
Alex Wellerstein has collected some early "Atomic editorial cartoons" at his blog.