Take a look at **[Calibre][1]** (for your PC)

 - freeware (opensource) and cross-platform
 - powerful and configurable e-books database
 - custom database fields
 - automatic metadata downloading from Amazon, Google Books, ISBN.org and other sources
 - compatible with many readers
 - web interface (only to view and download books)
 - supports many formats (even multiple formats for the same book)
 - editor for some formats (epub)
 - export database to different formats (CSV, BibTeX and others)

![enter image description here][2]  
Screenshot from [calibre-ebook.org][3]

On your iOS device you could use **[Marvin][4] Reader** and the [MarvinXD][5] Calibre plugin:

 - add/delete Calibre database books from Marvin
 - annotate books
 - view reading progress


  [1]: http://calibre-ebook.com
  [2]: https://i.sstatic.net/azkrJ.jpg
  [3]: http://calibre-ebook.com/demo#screenshots
  [4]: http://marvinapp.com/
  [5]: http://blog.marvinapp.com/post/61116544554