Although only one chapter of the book is actually dedicated to describing the battle itself, I still found this to be a fantastic read. In my opinion this is largely due to Adrian Murdoch's writing style - not dry and acamedic (like some other books on the subject), but instead, it is easy to read and is clearly intended for the non-expert.
Murdoch gives an excellent general description of the situation prior to Teutoburg, in addition to a more focused analysis of what the main personalities were doing up until then. After the chapter on the battle itself, he has written a few chapters about the immediate aftermath as well as the consequences it would have in more modern times.
Although I was a little disappointed regarding the lack of detail for the battle itself, Murdoch explains why he couldn't provide more - it simply comes down to a lack of information from ancient sources. I therefore think it's a little harsh to give him a lower rating based on this fact alone.