I updated all of my Kindle books to support the X-Ray feature. ATML and ATMH have lots of references, so it was great for them. It also seems to work pretty well for AFTHOTM too.
I had no other books in my Kindle library that supported it, so I wasn't sure how it was actually supposed to look.
I may have missed some of the references, so let me know if something important is not linked.