"Fantastic Adventures" was initially published in bedsheet format, the same size as the early sf magazines such as "Amazing", perhaps in order to attract fans who were nostalgic for the larger format. It started as a bimonthly, but in January 1940 began a monthly schedule. Sales were weaker than for "Amazing", however, and with the June issue the schedule reverted to bimonthly. The size was also reduced to a standard pulp format, since that was cheaper to produce. Sales did not improve, and Ziff-Davis planned to make the October issue the last one. That issue carried Robert Moore Williams' "Jongor of Lost Land", and had a cover by J. Allen St. John; the combination proved to be so popular that October sales were twice the August figures. This convinced Ziff-Davis that the magazine was viable, and it was restarted in January 1941—as a bimonthly at first, but switching to monthly again in May of that year.