Based on 'Great Stone Circles' I agree that Burl produces excellent coffee table books. However I would urge caution in accepting anything numerical he quotes.
It is also difficult to take seriously a scholar who rudely attacks the 'megalithic yard' of Professor Thom (after his death), for which there is good survey evidence, and then proposes his own metrics such as the 'Beaker Yard', the 'Cumbrian Yard', the 'Stanton Drew Yard', the ' Perth Yard', and the 'Cork Yard' apparently without any large sample statistical analyses. Burl's approach is based on an appeal to 'authority': his own opinion. Caveat emptor.

Professor D P Gregg (retired)