Importing epub as a node
It's in dev but the Epub module is probably your best starting-point.


  The new epub module for Drupal 7 provides displays for file entity and file fields and enables users to read epub/ibooks files inside their browsers like pdf module.


It doesn't import as a node, but you can take a lot of code from that module to build your own node-import version.

Interestingly, the reverse operation has already been implemented in Epub export, so you might want to have a look at the code for that one too.