We have used Spine extensively for our new book app: 12 Huia Birds.

The project has been supported by a funding body so that it can be freely available. It works on any Android or iOS tablet or phone device. Check it FREE here:

App Store: http://geni.us/huia2
Google Play: http://geni.us/android1

Project website: http://yoozoobooks.com/12huiabirds.html
Trailer: https://www.youtube.com/watch?v=qC26AweOVeA

Be great to hear your thoughts.

Thanks @BinaryCats. Yes, it's free as the production was supported by NZ on Air. Enjoy