When Microsoft killed Courier dead, they promised that "it will be evaluated for use in future offerings". One of those innovations appears to have been the iBooks-like "virtual page turn", which Microsoft applied to patent in January of 2009.
Of course, "innovation" is here used loosely, since there are other very similar technologies out there. Still, the Microsoft patent does seem terribly specific:
"One or more pages are displayed on a touch display. A page-turning gesture directed to a displayed page is recognised. Responsive to such recognition, a virtual page turn is displayed on the touch display. The virtual page turn actively follows the page-turning gesture. The virtual page turn curls a lifted portion of the page to progressively reveal a back side of the page while progressively revealing a front side of a subsequent page. A lifted portion of the page is given an increased transparency that allows the back side of the page to be viewed through the front side of the page. A page-flipping gesture quickly flips two or more pages."
Which is pretty much the iBooks experience. Of course, Microsoft hasn't been awarded this patent yet. But if they do, they could carve themselves a pretty nice slice of the iBooks pie. [USPTO via GoRumors]