The first edition of the Encyclopedia, whose founder was released in 1979, and had over 700,000 words. A second edition appeared in 1993 and contained over 1.3 million words. Both editions won the Hugo Award from the World Science Fiction Convention, in addition to numerous other honors.
This is one of those cases where offering the same content online very likely won't affect the same of the print edition. Virtually all the details in the ESF can also be found in Wikipedia and elsewhere. If the ESF offer it online, they will capture some of the attention from their online competitors and possibly gain sales.
image by xjyxjy