The book includes lots of postal history from the very first postcard and for the next 50 to 100 years. If you want a book that takes time to read and read again this is a great book. It talks about post offices, royalty, ships, World War 1, artists and illustrators, postcard clubs and lots more all in great detail.
The section that I really use a lot is in the appendix. There is the usual information about how to date postcards etc, but I like the list of the early Publishers of postcards and what trademarks they used and if they had series postcards. Lets say you wanted to identify a card by Gale & Polden Ltd. The book illustrates the trademark used on the cards. If they don't have an illustration they often describe the publisher markings to look for.
This book was published and copyrighted in 1971.