The weapon that can destroy humanity had a rather innocent beginning, with James Rutherford's genius experiments which demonstrated the existence of the atom, which no microscope is strong enough to allow us to see. In The Making Of The Atomic Bomb, Richard Rhodes takes the reader on a journey from the beginning of the identification of the atom to the massive destruction of Hiroshima and Nagasaki.
The science behind the whole process was a rather collaborative global effort, right up until the war. Scientists shared their work through journals, seeking to one up each other, challenge each other, and generally better understand the nature of the atom. When war came, every country thus had a pretty good baseline of what was possible, but then everything shifted into secret. The Allied Forces were fearful that Germany would come up with the bomb first, Germany was behind the pace but on its way, while Japanese scientists couldn't convince those in charge of budgets to proceed with the necessary research.
Of course, Germany could/would have been a lot more advanced if it wasn't so hostile to its own citizens, some of whom fled and worked against them. But I guess then Nazi Germany wouldn't have been the Nazi Germany we all hate if it was the type to treat its citizens equally.
The book is long, at well over 700 pages, and introduces a great number of people who made both large and small contributions to the advancement of the technology. I found it hard to keep track of everyone, and eventually gave up trying. I found the science more interesting: how some genius figured out that the old model was wrong and a new one was needed, how elements can be changed into other elements, and how elements are broken apart (or joined) in order to give off large amounts of energy.
Knowing what I know now about the science behind fission and fusion, I'm surprised more progress hasn't been made towards converting elements into valuable other elements (like let's say gold, ignoring its recent price drop). Element transmutation was what atomic physics was originally all about, before it became clear that it also had a more ruthless application. Maybe someday!
For history buffs, I think The Making of the Atomic Bomb is a must read.