Recently I noticed strange behavior with the “Add to Wish List” button on Amazon.com.  When I already added the book in my wish-list, why I keep seeing this button, why there is no UI indication that the following book is already added in to my wish list?

In my opinion there should be a Text Blurb that says “Item you are trying to add already in your Wish-list” and a little link that takes me to my wish list. Instead when I click on the Add to Wish List button and then see the already exist message.

Just my UX Two Cents.