The European Federalist Papers for generic eBook readers.
For free download, you will be redirected to Smashwords bookstore.

The European Federalist Papers for Amazon Kindle eBook readers.

The European Federalist Papers for iBooks on an iPad or a Mac. It contains interactive contents and other extra information.
For free download, you will be redirected to Apple iTunes bookstore.

The European Federalist Papers for reading on a large screen or print. It has the same content as the iBooks version, except the interactive parts.