I'm having the same problem. Here are screen shots. This first one is the Publish Online version. The transparency in the gradient feather (vertical, along spine in center) is not working and instead cutting off pieces of images (light orange box behind header and keys near margin).
Here's how it's supposed to look, in a screen shot from an Export to Interactive PDF file:
I've branched this to a new discussion since you replied to a year old thread.
You may well be expecting too much. Remember, this is all done with HTML and CSS which, while incredibly powerful is not quite as pixel perfect as other formats.