Bookcase app for iPhone and such?

I DON't WANT AN APP THAT YOU BUY AND READ BOOKS!
I want an app where I can type in a book I have or have read, and to just keep track
Like a book log
Preferably free, but I'll take anything with those requirements

It's not an app, but I use Librarything for this.
http://www.librarything.com/

You can also use Goodreads.
http://www.goodreads.com/