One wonders if the word 'definitive' can ever actually be applied to anything at all (in the sense that it is truly decisive, unconditional and final).
Hang on a mo though, the OERD goes on to define definitive (of an edition of a book etc) as "most authoritative." Yeah... I'll go along with that, but how long is anything the most authoritative?
Good luck with your book though Andy - maybe see you in Cambridge.