Since I e-mailed the following correction on December 25th to Paul Hoffman's website http://paulhoffman.wordpress.com/kings-gambit-corrigenda/, no one else has unearthed any mistakes.
Before Chapter 6 [Anatomy of a Hustler], the correct quote from Sherlock Holmes is “Amberley excelled at chess…”, not “Amberley excelled in chess…”, as given. To confirm this, go to http://www.amk.ca/quotations/sherlock-holmes/page-11.