the first book published by ace was a pair of mysteries bound "tête-bêche": keith vining's "too hot for hell", backed with samuel w. taylor's "the grinning gismo," for 35 cents, with serial number d-01. a "tête-bêche" book has the two titles bound in opposite directions, so that there are two front covers and the two texts meet in the middle (sometimes with advertising pages in between). ace did not invent this format even though they are well-known for it. ace published hundreds of titles bound this way over the next twenty-one years. books by established authors were often bound with those by lesser-known writers, so that this would help new writers gain readers. the main drawback of the "ace double" format was that the two books had to fit a fixed page length (usually totalling between 256 and 320 low-height pages); thus one or both novels might be cut or revised to fit. despite the tag "complete and unabridged" on the cover, books so labeled were sometimes still abridged.