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.
AlReader - Alreader.com - new perspective on reading e-books.
Dropbox - Online Sync and File Sharing
iReader - iReader is one of the most accomplished ways to read the books right from your smartphones.
Google Drive - Access and sync your files anywhere
Cool Reader - Fast and small cross-platform eBook reader for desktops and handheld devices
Mega - Secure File Storage and collaboration