L’Esperluette, which I found at my favorite Paris bookstore, La Hune, is the story of the and sign (&) and the word et from whence it came. It is published by Typographie Expressives, the publishing wing of Massin, graphiste, affichiste, journaliste, éditeur et écrivain.
The ampersand or esperluette dates to the 1st century A.D. The Old Roman cursive letters E and T were written together to form a ligature. In the 7th century, development of the Latin script and Carolingian minuscule, ligatures in general diminished, but et sign continued to be used and gradually became more stylized and more abstracted.
Jan Tschichold also wrote about &: The Ampersand. Is Origin and Development (1957).