Nice review. In particular, I'd like to draw attention to your point that much of the book is speculative - and while that's fine as far as it goes, it is not made terribly clear, which is more than a bit naughty on the part of the author and Osprey. As a aside note, I've read other Osprey titles that, alas, fictionalise history in this way. It's as if (in some titles), they don't think the reader can handle the concept of "we don't know", which is pretty fundamental in ancient history, and instead present one possibility as established fact.
So, even knowing the author had made a lot of it up, (e.g. it's pretty obvious that the conversations between the Roman commanders, and their reasoning, is invention) I was left a bit confused as to which elements are pure speculation and which come from solid evidence (presumably some of the survivors must have briefed their commanders, and that may be reflected in the ancient historic accounts, but the book doesn't state what comes from the historians, and what is made up - there's not really any excuse for this - a few footnotes could have improved things immensely).
I'll definitely pick up the AW magazine special edition that you mention, as I suspect this will help me sort out what actually happened from . For readers interested in this battle, I'd recommend the Ancient Warfare Magazine podcast on the subject, which is well worth listening to, and isn't afraid to stress what we don't know (i.e. most of it!).