For hosting common files it's ok. Also it is on Android too do, great to transfer files between your Windows and your phone. But if you want better security you have to subscribe a monthly offer.
calibre - Ebook manager, viewer & converter
Dropbox - Online Sync and File Sharing
FBReader - FBReader is an e-book reader for various platforms. Features:
Google Drive - Access and sync your files anywhere
Google Play Books - Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
Mega - Secure File Storage and collaboration