Karl Baden, a photorgapher and teacher at Boston College, likes to spend time browsing through book stores.  He was struck how many book covers featured well known photographs.  He was also surprised by the variety of books that would feature the same image - books that otherwise had nothing apparent in common.  As his interest in the subject increased, he began buying books for their covers.  His collection was featured in an exhibit at Harvard's Carpenter Center, which ran through November 13, 2005.  The exhibit illustrates the variations of the same photograph as featured on different books.  As this article explains: "The same photograph might be cropped or tinted or have type on it.  In those various uses, the covers became a kind of history, at once revelatory and warped, of not just photography but also book design, literary taste, and marketing considerations."