Mark Twain was a roving reporter for a few American newspapers when the Innocents from the New World went on a cruise to the Old World.
They visited the Azores Island, Gibraltar, Morocco, Athens, Italy, etc, and the Holy Land.
This book has all the 58 letters he sent for publication. The annotation is only in respect of which line in the letters was edited or deleted from the book that Twain wrote in return. The book is The Innocents Abroad.
I find the annotation rather irrelevant. It serves no useful purpose to the general public. A better format would be to give notes that provide context and comments on Twain’s letters.