This is one of a series of Osprey books by Duncan Campbell. Essentially, this is an overview of the techniques and equipment used during the period. There is a mixture of evidence drawn together; contemporary texts, archaeology and a mixture of actual scientific knowledge combined with practical experimentation. There is not a great deal of secondary source material available on the subject of ancient siege warfare and this is a very solid beginning. This is a relatively technical and yet very readable work, with a mixture of narrative and analysis. This could easily be a very dry subject but Campbell brings it to life admirably.
The colour plates are very good; they display the sheer scale of the machines and add vividly to the text. Adam Hook is a good choice to illustrate the text.
Of course, I have to complain at the lack of decent maps; why won't Osprey add a couple of maps at the back of each book? Still, the ones supplied are actually much better that Osprey usually provide. Some of the places in the text are actually named!
I suggest this book should be read along with the new Roman Siege Warfare, Greek and Roman Siege Machinery and Greek and Roman Artillery, all by written Campbell and published by Osprey. Without doubt the best current work on the subject of ancient siege warfare. Well recommended