Not a book for reading cover-to-cover. Unsurprising maybe, given that it is largely based on a PH.D. thesis.
I think I expected the (very many) maps and diagrams to be clearer as well. A real criticism is that It is often difficult to place sites in relation to roads and any towns/villages. Indeed very many camp remains have only a local name attached and it requires a diligent search to ascertain what part of the country they are in.
Worth having for reference, although - and this is no reflection on the author - very many of the "sites" appear to be near fancifully described as forming parts of Roman camps and are certainly not worth trying to find.
I think my money would have been better spent on one of the several works on legionary fortresses around the UK as, although it is incredible that any traces remain of temporary marching camps, often thrown up by legionaries in a few hours of trenching and construction after a day's march: these traces are evidently highly insubstantial.