Issuu was the first "flipbook" type of software I ever paid for. I used the free version for a while to get the feel of the product and then upgraded. Issuu is great for making page-turner flipbooks from static pdfs. Really easy to use. Upload and hit convert, basically. There are ways to load hotspots in the publication (so people can click and go to webpages or it opens your email etc) They also have a nice set of options when it comes to embedding the finished product afterwards (incl small videos etc). One of the features I like is adding the magazine (publications) to stacks (or groups). You can then feature those groups on a display shelf for people to see (however many you want to display) and click on. Good solid service and reliable.

Interactiveness of what would otherwise be a static document PDF

I love that I can get custom recommendations for magazines that cover topics I'm interested in, and also that I can create my own publication stacks based on categories and industries I'm interested in. It's a great way to get fresh ideas from a written/story perspective as well as ideas from a visual/design perspective.