I don't know when I last picked up an encyclopedia and read it cover to cover, but I did this one. It was truly fascinating in its depth and understanding. I spent more time on Volume One, Chemical and Biological Weapons because I know less about them than the Nuclear Weapons covered in Volume Two. I can't swear that the information in Volume One is totally accurate, but the information in Volume Two is dead on. And therefore I have to presume that Volume One is the same. The books cover everything from the earliest experiments and incidents to very recent data. There are hundreds of entries, each written by a specialist in that particular area. The entries on World War II alone cover an amazing amount of material that simply isn't generally known. This includes things like the Japanese Unit 731, the Porton Down research establishment in England, the production in the United States of 150,000 tons of chemical warfare agents as well as bacterial warfare agents containing some pretty nasty things like Cholera, Anthrax. Another tidbit that I didn't know — The strain of Anthrax used in the 2001 incidents was one produced at Texas A&M for the US Army researchers. As I said, my knowledge in this area is weak. So perhaps this was more commonly known, but it was a surprise to me. On the nuclear side virtually everything is covered from the first design work in World War II to the North Korean Nuclear Weapons Program's announcements in 2002. If I have to pick out anything wrong with these books, it would be that I noticed one or two typos. And of course, I would like to see even more included, a good report on the SL-1 reactor accident for instance, the biggest (non-bomb) radiation leak in the US. To be sure you can find out about this on the web, and where do you stop when your book is already over a thousand pages. Very highly recommended.