The site operates like a bookshelf. You can search or browse the library of uploaded content (that users make public), and can then bookmark the content - anything from presentations, to catalogs, to newsletters. This adds it to your 'shelf,' where you can organize things into folders (like most email programs), or share, or download.
The makers of Issuu pretty much hold your hand through the whole process with little videos, which is nice. Plus, the website interface is simple and easy to use anyway. One of the coolest things, though, is that you can implement their slick document presentation on your own site. Haven't come across any sites using this feature yet, but I'm testing it out offline.
