Apple and Kaplan publishing are giving away 100 book titles as part of back-to-school/Learn Anytime, Anywhere promotion this week. You have to access the store and the list of free titles from inside the iBooks app, which runs on the ipad, ipod touch and newer iphones. I've included a few more details and the complete list of titles available on
this blog post.
The promotion is only valid Aug 24-30, so be sure to grab any that look interesting (but note that the ones I've tried so far seem to be stuck in a pre-order status).