Tumblebooks just recently added the ability to view over 40 of its books on iPads! To see them, click “Story Books.” There currently is a link at the top of the page that says “Click here for iPad compatible titles.”
When you navigate to Tumblebooks from an iPad, go to that link and then above each cover image is a link that says “iPad.” The video first appears to be a small black rectangle, but after starting it, the fullscreen button will appear.

