It appears the markings and writing on the inside cover are actually supposed to be there and are part of the book's design. These are handwritten letters between Berenson and Marghieri. A very intimate insight and a book originally published with great care.
Bernard Berenson (born Bernhard Valvrojenski) was an American art historian specializing in the Renaissance. He was a major figure in pioneering art attribution and therefore establishing the market for paintings by the "Old Masters".