A good full color, multi-media, touch screen device for reading e-books — which the iPad now is — implies something about how electronic books should be conceived.
Electronic books should not simply be print books made accessible in electronic form. Rather, they should be conceived and created to take full advantage of what a device like the iPad makes possible, while remaining true to what a book is and what a book is for.
I have lots of thoughts on this I may post if I have the time. In the meantime, TechCrunch also has a post which begins to offer some thoughts on this.