Bookshelf 2.2.0 and Universal Viewer

[cslds]

I am running Omeka S 4.1.1 and I am trying to get Bookshelf working the way it does on your site.
I have downloaded the Bookshelf theme but when I add my PDF to Universal Viewer it shows only 1 page at a time not like yours which looks like a flip book. Universal viewer will show images in two page format.
Am I missing a step or am I doing something incorrect.

I would greatly appreciate some guidance on this issue.