Book-Trading Post Opens on a Brooklyn Sidewalk Marilynn K. Yee/The New York Times The Little Free Library on St. Marks Avenue in Prospect Heights aroused the curiosity of Elinor and Evan Bither. From a distance, it looks as if it could be an unusually large mailbox, or perhaps a doghouse almost three feet off the ground. Tucked under the shade of a tree and bolted into a sidewalk on St. Marks Avenue in Brooklyn, this wood box, 20 by 24 inches, turns heads as neighbors stroll by. Children are, of course, more willing to explore. On Monday, the siblings Evan and Elinor Bither, moving by on their scooters, halted to a stop in front of what has quickly become a fixture in Prospect Heights. Evan, 6, turned a wooden latch to open the glass front door. He had come to New York's first official Little Free Library. Evan flipped through the collection: eight novels by Patrick O'Brian, a book by Elie Wiesel and "The Night Remembers" by Kathleen Eagle. Why are there only grown-up books in here? Evan said. Alas, it is one of the difficulties of a library shared by all. The collection, limited by its compact home and the supply of donations, is ever changing. But many neighbors say the absence of children's books on Monday was an anomaly. The Little Free Library, whose slanted roof carries the messages "Saint Marks Children's Book Stop" and "Take a Book, Return a Book," was opened at the end of May. Its housing was provided by the national Little Free Library organization, which estimates that there are 2,200 such places, across almost every state and about 30 countries. Each local library pays $25 to register with the group. About 20 percent buy the wood box from the national organization, which can cost a few hundred dollars. The rest, using materials like canoes or ovens, make them for themselves. The movement, which began in 2010, has been slow to take hold in New York City. But its founders say that once it catches on in a big city, as it has in recent weeks in Los Angeles, the number can shoot up. The founders, Todd Bol and Rick Brooks, started the nonprofit venture in part to help encourage reading and to improve literacy, but they say the libraries also can quickly become a hub for the community. Suzanne Pettypiece, 35, brought the library to her Brooklyn street. After struggling to get a clear answer from the city on whether she could affix the library to the sidewalk outside her co-op, at 185 St. Marks Avenue, she just installed it. "I figure if I get opposition to it, I'll just start a petition or something," Ms. Pettypiece said. Richard Leong, the treasurer for the building's board of directors, said there were initially some logistical concerns. For example, some building residents worried that too many people might congregate outside the building. But he said, "After discussions, most people on the board and in the building seemed pretty pleased." Ms. Pettypiece said that from her third-story apartment, she sees children come running by the building. "They'll pause and take a book and keep running," she said. It's pretty amazing to see. Several neighbors said they welcomed the installation. It's a marker of the increasing friendliness. It offsets some of the new, young commerce," said Ryan Taylor, 41, who has lived in the neighborhood since 1988 and planned to donate a copy of "The Little Prince" by Antoine de Saint-Exupéry. "It's real and it's humble."Siddhartha Sanchez, 35, said the library had introduced his children - Zion, 8, and Hannah, 6 - to new books. Zion took up the Hardy Boys, and Mr. Sanchez had to require his daughter to take only one book at a time. Now, she often sits on their stoop reading a book, cover to cover, until she is ready to return it to the library and trade it for another. Mr. Sanchez said the library had taught them valuable lessons. For example, he asks them to donate books to it, teaching them the value of sharing. "People feel books are part of their heart and soul," Mr. Bol said, "but if they could share them with their neighborhood, it's like sharing a part of their self."