All books can easily be shared through social media with a rich experience. eBooks can also be previewed through social media. See: Can My eBook Preview be Viewed Within Social Media Sites?
However, the entire purchase experience does not happen through social media, as users are directed back to the Aerio platform to complete their purchase.
For ebooks, we are in the process of updating our previews to be purchase-enabled, where the user can complete the purchase experience without ever leaving a social media app. Stay tuned!