For almost all manufactured goods which the manufacturer doesn't sell directly to the end consumer, the manufacturer sells to a distributor, and the distributor is then free to resell the good to the consumer at whatever price she wants (although of course if the distributor wants to stay in business, then the final price will be primarily set by market forces).
But the market for books is an exception: the manufacturer (i.e. the publisher) physically inscribes the sale price directly onto the manufactured good. The distributor (i.e. the physical or online bookstore) can offer a "discount" and sell it at a lower price than the prescribed one, but can't reasonably sell for a higher price for reasons of consumer psychology. I can't think of any other good which uses this strange business model. It seems to deprive the market of pricing flexibility to adapt to e.g. regional variations in demand, transportation costs, etc.
Of course, the market for books is very distinct from a standard market described in microeconomics textbooks, because so much of the value of the book comes from intellectual property rights rather than from physical resource and manufacturing labor costs, which makes it more like a monopoly than a competitive market. (Moreover, depending on how the author's compensation is structured, the publisher may face very high fixed costs.) But on the other hand, other markets like video rentals seem similar in that respect, but the movie studio doesn't set the sales price - the video distributor does, as in a standard market.
Why is the market for books so weird?