More than 90,000 people downloaded Apple’s new book publishing tool, iBooks Author, in its first three days of availability, according to one analyst’s figures.

Released last week, iBooks Author allows users to publish interactive books with full colour photos, such as textbooks, cookbooks, history books, picture books, and, as one artist has shown, comic books.

The download figure comes from analysts Global Equities Research (published by Venture Beat), who also indicate that over 350,000 textbooks were downloaded from Apple’s iBookstore in the same period. Many of these may have been free downloads of a two-chapter section of E.O. Wilson’s Life On Earth, rather than paid downloads of full textbooks, but sales will be intermittent anyway as school terms and University semesters come and go.

The real test will be whether authors find iBook Author sufficiently convenient to make up for the stringent End User License Agreement, which decrees that if the author wants to distribute their book for a fee, they have to go through Apple.

EULA blogger Ed Bott calls the iBook Author license agreement ‘mind-bogglingly greedy’ in a post on ZDNet, saying it’s like Microsoft asking for 30% of a public speaker’s fee if he or she uses PowerPoint in a presentation.

"What I see so far makes this program and its output an absolute nonstarter for me,” Bott writes.

Do you think it's fair to prohibit publishers from selling work created in iBooks Author outside of the iBookstore? Post your comments below. 

Update: Apple CFO Peter Oppenheimer revealed in a conference call discussing the company's quarterly results today that over 600,000 copies of iBooks Author have now been downloaded since its release last week.