I've had a lot of offline discussions with readers about this subject, so I'm adding this post to put the information front and center! Here's the lowdown, which I have also added to our web site:
High Definition and Interactive!
iBooks provide a superior reading experience because they include embedded HD-videos, high-definition images, and interactive diagrams--none of which Amazon allows in Kindle books. So, if you own an iPad or Mac (running Mavericks), we highly recommend purchasing the iBooks version of this series.
Seamless Automatic Book Updates
Apple has a superior process for providing book updates. When we release an updated version of one of our books (we provide free updates on a regular basis), Apple alerts you by displaying an update badge in the iBooks app. You just tap the badge to download an updated version of the book.
All the best!