Of course, there are a lot of books at amazon. To find a specific book, you have several possibilities. Either you try the 'search'-frame (be careful to write your keywords in the correct way as they do appear e.g. in the title) or you try to follow the categories and the proposed selections (Top10 lists, etc.) of books there. A great feature of course is the similarity based search or the search based on recommendations. This is the only way to discover something new by serendipity, something you did'nt even know to exist . In real life this way to find a book comes equal to finding by recommendation of friends or by your local librarian or book seller.
But, what about good old window-shopping. If I come to a bookstore or to a library, I love to wander around the book shelves and to look here and there and to spend (sometimes to waist...) lots of time.
Something that comes visually close to this experience is zoomii.com. It's an amazon add-on for browsing (a considerably large set of) books (they say its about 20.000 books right now) with the look and feel of book shelves, ordered by categories, with (right sized) book covers in the shelves. You can walk around, zoom in and out, and of course you can browse by categorie or search via keyword.
It's really some nice way to visualize large sets of documents. I would like to see an API for visualizing documents on the web that way!!