Thanks must go to the guys at We Made This for the tip-off. As St Bride Conference attendees they got a copy of Jeremy's lovely 2004 TypeBookOne for free. I've just bought mine and it's well worth the micro price tag.
As well as samples of Mr Tankard's superb typefaces, it includes a text by Catherine Dixon on "the emergence and use of the type specimen" and a short text by the man himself on the OpenType format.
According to his "occassional newsletter" Footnotes, stocks are running low but you can order a copy using this form. It also reports that TypeBookTwo will be going to press soon.