This book is sad. If you are easily upset or have a weak stomach, it's probably best that you don't read it. Seriously.
That being said, this book is valuable in that it describes the days after the Hiroshima bombing in painful detail. The first fifty pages or so deal with the bomb actually dropping, but after that, it is just what happens to the people. I thought that was interesting.
While it deals mainly with what happened between the Hiroshima bombing and the end of the war (August 6-August 15), it is written in such a way that the main character is copying his journal of those days so that he can donate the manuscript to the local library. It's an interesting premise, so you can understand how the people felt about it during and after the fact.