The 2022 edition, number 28, will arrive this year in December. Primarily responsible were the familiar names of Donna Houseman, Bill Jones, and Sergio Sismondo. Based on an article in the November 15, 2021 Linn's, it appears that price changes account for the majority of what is new.
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.
