hit the App Store last week, and the appt promises to unleash a new idea-driven book to users every two weeks. The app itself is free to download, but the books arent. Users can either pay $15 for a three-month, six-book subscription, or they can instead take the a la carte route and pay $3 per title. Users who subscribe within 90 days of the apps launch can download the entire roster of books at no additional charge.

The books themselves range beyond mere text versions of the famous TED Talksthey include audio, video, and social-networking features. Most TED ebooks contain fewer than 20,000 words, and are designed to be read in one sitting.

TED Books is compatible with all devices running iOS 4.3 or later.