Initially these were mostly in tête-bêche format with the ends of the two parts meeting in the middle and with a divider between them which functioned as the rear cover of both (the two parts were oriented upside-down with respect to each other in order to effect this), but the company also published some single volumes during the early years.
For more information about the history of these titles, see the entry for Ace Books, which includes a discussion of the serial numbering conventions used and an explanation of the letter-code system.
For more information about the history of these titles, see Ace Books, which includes a discussion of the serial numbering conventions used and an explanation of the letter-code system.
The double format inspired contests for ironic or satirical combinations of titles that might appear, as in "No Blade of Grass"/"The Sheep Look Up".
[citation needed] "It's a fond legend of fandom that if an SF editor got his hands on the Old and New Testaments, they'd be published as War God of Israel and The Thing With Three Souls.The following references have not been reviewed: