Some 40,000 college students studying on a Flat World

I interviewed CEO Eric Frank a year ago about his plan to deliver e-book textbooks free to college kids, and about the business model he claimed would still spin money for the textbooks' authors.

In March Flat World got $8 million in funding, and the news is they now claim 40,000 kids are using their stuff.

This is the tip of the iceberg, David Weir of BNET writes. The number could grow five-fold in a year and the total market is 17 million students.

So far the company has focused solely on business and economics textbooks. But it now has 32 titles in development covering basic subjects like psychology, sociology and genetics.

Instead of paying $100 for the textbooks you need in a class, Flat World claims its customers pay an average of $18. In addition to the free download students can buy a PDF version, a printed version (black and white or color), even an audio version. (My eldest is dyslexic -- this is big news.)

Flat World is being followed into the market by a host of competitors, like Chegg and BookRenter. This may be the best news of all.

While the material is subject to copyright, it's called open source because it's freely available for download on the Internet.

When I spoke to Frank last year he mentioned several other ways to monetize the content, from testing guides to online chats with book authors. So you might think of this as more of a Priceline model. Students can name their own price for textbooks, actually spending more than they do now if they want ancillary services, or spending nothing at all.