When we think of a library, we picture a building on a street or perhaps a room in a school. But some libraries aren't kept behind four walls. Some move from place to place in the most remarkable ways: by bus, by boat, by elephant, by donkey, by train, even by wheelbarrow. These unusual mobile libraries are often the only way that books can be brought to people in remote areas, such as the mountains of Thailand, the Gobi Desert of Mongolia, or rural areas of Zimbabwe. In places such as these, the arrival of the libraries is a major and much anticipated event. But the books would never reach the people without the hard work of dedicated librarians and volunteers.Margriet Ruurs, writer and educator, contacted librarians around the world and asked them to share stories about their libraries. In many cases, volunteers and librarians took camera in hand to photograph their mobile libraries and to record the happy faces of children receiving books. The result is this inspiring photo essay, which is a celebration of books, readers, and librarians.Why would librarians go to the trouble of packing books on the backs of elephants or driving miles to deliver books by bus? Because, as one librarian in Azerbaijan says, "the mobile library is as important as air or water."