This was an interesting run through of what's known (precious little) from an academic POV. It is very much rooted in the provable with archaeology and scholarships to the front. Consequently that spark of enthusiasm, the thing that interested the authors in the period in the first place, has been dampened and doesn't come through. From unbiased academia it's understandable.
But there are other things that are missing, the people, how they farmed, the sea and ships. This last especially. There was a lot of focus on the northern and western isles, there was talk of sea piracy against the Romans (I'll get back to that), but barely a mention of going down to the sea in boats.
There was mention of artefacts' found in bogs but a fuller run through of the clothing likely given the sottish weather would have been interesting. Likewise a run through of the farming year.
There is play made on the book cover as the Picts being scourge of Rome, a proof on the artefact found in Germany, but what, when, how?
The finding of Pictish site in the low lands seem to be hit n miss depending on crop marks due to the agricultural improvements. There most be known roads/paths whatever between known sites and the sites themselves which could be extrapolated to map out. I find it hard to understand, given the place names, stone distribution etc across Aberdeenshire (as is) that it doesn't feature in the narrative more. This seems to be a reflection of the lack of documentary evidence.
So this is a picture of what's known rather than a rounded picture.