Notwithstanding the fact that Paul Tibbets has passed away, since those days in August 1945 no other nuclear weapons have been used in war, indeed virtually every mention of any nuclear capability since, be it civil or military, is still compared with either Hiroshima or Nagasaki i.e. 'This weapon is equivalent to 20 Hiroshimas'. Yes it was very very nasty, yes it ended WW2 a lot earlier that was predicted, yes it saved a lot more lives than it caused, but most importantly it showed the world the true horror of nuclear weaponry.
I also recommend the book 'Ruin From The Air', which tellls the story of the Manhattan Project, and if you're ever in Albuquerque pay a visit to the Atomic Museum.
Finally, lets not forget that Leonard Cheshire was an observer on the Nagasaki B-29, and this experience probably led him towards his lifetime of charitable work along with his wife Sue Ryder.