McCormick's range and breadth of scholarship is remarkable and undeniable. I was thoroughly impressed and found myself a bit awed by his exhaustive research.
I loved the book overall, but I found myself questioning some of the connections he made. It is possible, as he concludes, that Goths in Spain in the 7th century were conscious of imitating antique Roman and contemporary Byzantine triumphial ritual. But it is also possible that the Goths were celebrating a victorious battle in a way that wasn't at all conscious of these things and was simply reflective of the culture they lived in.
I felt often that the connections were tenuous and that obviously all kings in all times and all places celebrated their victories often with parades or parties in their capitals and it would be possible to analyze a Chinese Emperor's victory celebrations as imitating Roman traditions if you didn't already know that wasn't possible. Surely, the Carolingians and Lombards had a lot more cultural contacts with Romanized peoples than the Chinese and surely some of the ritual obviously descended from the late antique triumph but my personal conclusion is that there was a lot fewer examples of conscious imitatio imperio than the authors would assume.
I don't mean to be negative because I greatly enjoyed the book and learned quite a bit. I came away from it deeply impressed with McCormick's painstaking research. It is an extremely specialized topic and definitely a scholarly work that isn't suited for mainstream lay audiences, but anyone who is interested in the topic would greatly enjoy it.