For whatever reason, prices are down again. Amazon at $68.23. Barnes & Noble at $69.15. Book Depository at $68.22 with free shipping worldwide. And you can still get 20% off at the publisher with code LYON2017 (that's $64 or £44, plus shipping).
Still looking for more reviews on any site where you might have bought one, please.
Update: those discounts didn't last; but maybe they'll be back.
Nov. 9 update – Amazon's and Book Depository's lowest price yet: $62.05.
Jan. 1 update – The publisher has sent an updated code good for 20% off through 2018: [not surprisingly] LYON2018 at checkout at their UK or US site. Amazon's price is only 10% off today.