[DMSmillie]

Adding to my post above -

When you get to that add-on page after the last page in a book, it says:

You've finished. Before you go...

Tweet/share that you finished this book

Rate this book

Customers who bought this book also bought:
[list of links to other books purchased by customers who bought the book you just finished]

To do anything, you have to actively click on one of the links.

If you click on the "tweet/share" link:

You get a popup box which has a "pre-typed" message:

finished book_title by author

(with the actual title and author)

You can edit the message if you want before clicking on SHARE (there's also a CANCEL option). Additional text in the popup box informs you that a link to the book will be appended to your message.

If you click on SHARE, but haven't previously entered your FB/Twitter login info, it pops up a message saying you have to enter that info in order to use this feature, and provides a link to the settings page (it says there'll be a link back from there). Again, there's a CANCEL button at this point.

I'm not about to create a Facebook or Twitter account simply to see if this feature "auto-shares" to my account even if I select CANCEL, but seems to me that, short of Amazon doing silly things for no apparent good reason, it'd be pretty well impossible to accidentally post details of what you've been reading.

If you select "Rate this book", you get a small popup box with 5 stars (you can select as few or as many as you want), with buttons to CANCEL, SAVE & SHARE, or SAVE.

If you just select SAVE, as far as I can see, it simply saves your star rating, and now displays it on the "now you've finished" page, alongside the "Rate this book" link.

If you select SAVE & SHARE, you get the social media popup box, with the pre-typed message:

just finished book_title by author and gave it x stars"

with the same options as described above.