I really cannot understand why anyone would give this 'work' - if that is the word for it - any rating above "1". In fact, if it was possible, I would not even have given it one star! This type of "history" is a menace. I can only conclude that people who give this volume any sort of rating at all are themselves totally ignorant of the material in question. Either that or they are being very kind and do not want to offend.
D-C has now written a number of these "Roman Army Histories" and all of them suffer from the same faults - indeed they are often repeated throughout these volumes, with no attempt that I can see to make any corrections at all. Some of the errors are relatively minor - a date missed by one year or a town with a slightly different version of the name perhaps - but there are others of a much more fundamental nature that cannot be excused as mere slips of the computer keyboard. The contention on the jacket 'blurb' that this man has spent 30 years 'researching' the Roman Army is laughable in the extreme. Whether the book 'reads very well' (as another of the generous reviewers here has stated), is irrelevant. If the information is wrong then it doesn't matter how well it 'reads'. Rubbish is rubbish, however well you dress it up in prose.
The assertions that this man makes, with not a shred of documentary evidence for them, are staggering. One of the most serious of these is his contention that the Roman army enlisted its legionary soldiers at fixed intervals and that it is therefore possible to calculate exactly how old the various batches of legionary soldiers were (rather in the manner of the Zulu impis, it would seem). If this were to be true it would mean that virtually the entire Roman army (or at the very least, a goodly portion of it) would have to be replaced en bloc, since the majority of the legions (according to him) were originally raised at more or less the same time, either by Caesar himself, or Pompey! This, of course, is rubbish. It was only in early Republican times that legions were raised in this manner - but only for one year of campaigning as the soldiers were peasant farmers who had to plant and tend their crops. Once an empire was formed, this mode of enlistment was impossible as legions would be stationed outside Italy for years at a time, sometimes decades. Even in Caesar's time this could not have been the case. Look, it took EIGHT YEARS for the man and his army to conquer Gaul!
I could go on, but this would be very boring to everyone. The text is littered with fundamental errors, contradictions of known factual information, idiotic assertions for which there is no proof cited (and none to be had either). In terms of legion 'histories' I counted at least two dozen erroneous statements (before I gave up counting). These are not simple 'slips' - they are things like denial of existence (i.e. missed from the roster), wrong postings, wrong names used, etc. The idea that each legion had a specific shield blazon and that we know which legion had which, is arrant nonsense. Attempts have been made to equate the designs seen on Trajan's Column with legions involved in the Dacian Wars but these are only tentative and cannot be confirmed. It's guesswork, not fact. And that just about sums up Dando-Collins' approach - if he can't find evidence, or doesn't know it - he just makes it up because it 'sounds' OK.
If you want to know how the Roman Army was run, what happened to the legions, where they were raised and based, etc. then there is any number of books out there, written by people who DO know what they are talking about. Read Andrian Goldsworthy, Lawrence Keppie, Mike Bishop & John Coulston, Jan le Bohec's monumental work on legio III Augusta (available in English) and so on. If you buy any of D-C's books, then you have only yourself to blame. It will only encourage him to write more of this tosh.