There is a free, short one written by EO Wilson. The rest are all $14.99. That is fantastically cheap. Some of the animations in the full bio book tell a better story than a full semester of cell bio used to be able to give most students. If you own an iPad you should nab the free one just for the experience.

They all greatly resemble Al Gore's Our Choice app in use. Interactive charts, videos and expandable pictures. It's really neat stuff to encourage student engagement.

This has the potential to be revolutionary, especially coupled with the Free iBooks Author software that helps anyone create e-books.