Readers will be able to see all of the books they purchased via Amazon, including both paper and digital, books purchased from third-party sellers but not ebooks purchased from Amazon's original ebookstore (those sales records are gone, I'm told). They can assign them ratings and add titles to to their bookshelves, or not. I'm told the import option will also let readers exclude titles that they don't wish to publicize.
This feature is not widely available, and in fact I don't have the option yet. According to the comments left by Goodreads reps on their blog post, that is because they are rolling this out incrementally.
If you're interested in giving it a go, you can check the My Books page. The option will be listed in the menu on the left - if it is available. If you don't see the option and you want to import your purchases, you can force the issue here:
I just clicked the link and went through the process, and I must say that I am relieved that the books aren't being added automatically. I have to rate or shelve each title before it will be added to my Goodreads profile, and that's a good thing because my mother shares my Kindle account. She has a very different taste in books than I.
Ever since Amazon bought Goodreads last year the retailer has been integrating the social network more closely with its bookstore. Late last year Amazon rolled out an update for the Kindle Paperwhite which added Goodreads integration, including the option to rate and review books.
The site now boasts 25 million members who added 294 million titles to their virtual bookshelves in 2013.