I've worked on an app that allows people to upload their photos to make actual photobooks. In this case it's nice to be able to show them what the book will look like. That app uses something in flash, but this HTML5 thing looks better.

Does the animation really add much? Would it just become annoying quickly?

While I agree with your first sentence, actually forcing my users to walk to a (virtual) book store is an old paradigm.

I believe the virtual book store example was sarcasm.