the cutting edge and the long tail

One of the great strengths of a library is that, unencumbered by the restrictions of retail, it can provide the "long tail." While it's true that a library's shelf space is finite, the fact that it doesn't need to sell, and sell quickly, to stay alive means that it can keep a wider variety of materials and can serve groups that the mainstream (not to mention the popular or the elite) ignores or shuns, or just deems unprofitable -- the shy, bookish types, the elderly, the poor, and people who are interested in "weird" topics or viewpoints.