Editorial changes new to this edition according to the Linn's article include:
--on cover listings for Alexandretta, Lebanon, Saudi Arabia, Somaliland Protectorate, Syria and Zululand;
--Algerian Parcel post stamps;
--Editorial notes in Andorra for stamps that were authorized but not issued;
--two French local stamps, Scott L1 and L2; and
--British inland mail local stamps under Madagascar.
I've made summaries for all previous editions that you can find via the search function.