It seems like opinions on this book are mixed. I quite enjoyed it as someone with a reasonable interest in military history but with no real expertise in the area.
The book covers 30 land battles that are intended to illustrate failure in five categories. The time period covered is long and the forces involved are fairly diverse, but there is a bias towards more modern conflicts (say in the last 150 years) and those involving British troops. That's fine with me as I'm more interested in those two aspects, but some people might think the view is a bit skewed.
Each example averages around 12 pages, which I thought was enough to explain what happened but not too much to drown in details. Around half of them contain maps, which generally aren't great, so it is sometimes hard to picture what's going on, especially as the text can sometimes be a list of which units attached which.
Overall, quite an interesting book but it could have been more lively.