Amazon bought together feature

Is awesome, and I can’t believe I haven’t seen this before. Rather, I’ve seen it, but haven’t noticed the functionality of it.

I always saw it as a way to upsell me to buy more books. It is that. But Amazon has also built some interaction in to this feature. You can click to deselect one of the books, and the page is AJAX’ed (I promise I won’t use that again), showing you the updated price for just two of the books. Neat!