This document published by Gizmodo explains Courier's interface, gestures, and features more in-depth than ever before.
Gestures: The basic finger gestures are exactly what you'd expect. A one-finger tap-and-hold clips content, one-finger flicks scroll vertically and turn pages. Two-finger gestures open and close apps: Up or down opens an app, while a swipe offscreen closes it. Flicking toward the other screen with two fingers slides it across. Pinches come into play, for zooming out from the Journal to the Library. These gestures can and probably will change to some degree, possibly incorporating more fingers.