Ace Double

The Ace Doubles were a series of books published by Ace Books, mostly under the editorship of Donald A. Wollheim from the early 50s to the late 70s. They consisted of two novellas or short novels (typically 75-125 printed pages) bound tĂȘte-bĂȘche, a format in which the book has two stories bound upside-down with respect to each other, with two front covers and the end of the two stories meet in the middle of the book.

The stories were often taken from the British SF magazines and were frequently heavily edited.