I never had to use the sync feature before, but now that I have the NC and the Touch, I have been using it and it can be a little frustrating.
From what I have tried, these are the steps I need to take to sync both devices:
This example is to sync the book that I am currently reading
I have to make sure I exit the book in the first device
Before opening that same book in the second device, I have to sync the library on the second device, then open the book
Otherwise, it won't open in the same page: for example, if I don't exit the book on the first device, even though I sync on the second, it won't open on the page I was reading
Hope this doesn't sound confusing, but the main point is that it not automatic at all. I don't use the apps so I am not sure how it works on those.