Economist book review - The Bombing War: Europe 1939-1945
Some interesting statistics in this article.
The article misses a point mentioned in one of the comments: "Not bombing German cities during WWII would have provided a gift worth many 10's of millions of man hours of industrial production and scientific research & development".
http://www.economist.com/news/books-and-arts/21586520-damning-verdict-bombing-campaign-europe-during-second-world-war-costly