Gizmodo has published a leaked video of the Microsoft Courier booklet, you can check it out over here.
The heart of Courier appears to what's called the "infinite journal," which is what it sounds like: A journal/scrapbook that is endless, bound only by storage constraints (presumably). Hopefully they will call it something less awkward. The journal can actually be published online, and it's shown here as able to be downloaded in three formats: a Courier file, Powerpoint or PDF. There's also a library that looks a lot like Delicious Library, where things like subscriptions, notebooks and apps, are stored.