Dos-à-dos binding

In bookbinding, a dos-à-dos binding (/doʊsiːdoʊ/ or /doʊseɪdoʊ/, from the French for "back-to-back") is a binding structure in which two separate books are bound together such that the fore edge of one is adjacent to the spine of the other, with a shared lower board between them serving as the back cover of both. When shelved, the spine of the book to the right faces outward, while the spine of the book to the left faces the back of the shelf; the text of both works runs head-to-tail.

The name is probably a reference to a move in square dancing (known as dos-à-dos) in which two dancers face each other, then step forward and then left, until they have right shoulders adjacent; then move to a position where they are back to back, then move to have left shoulders adjacent, then return to facing each other.

The dos-à-dos format dates back at least to the 16th century, though they were most common in England in the first half of the 17th century. Two books frequently bound in this form were the New Testament and Psalter, which were both needed during church services. Regardless of content, the outer boards of dos-à-dos bindings were usually embroidered, or covered with leather and then finished with gold.

One example is Irvin S. Cobb's Oh! Well! You Know How Women Are! bound dos-à-dos with Mary Roberts Rinehart's Isn't That Just Like a Man!, as published by George Doran in 1920.