These are Little Free Libraries.
Each of them is designed to hold about 20 books and runs on the honor system Take a Book, Leave a Book. Asked if people try stealing the books, Rick Brooks and Todd Bol - founders of Little Free Library - get surprised: “But you can’t steal a free book.”
50 Little Free Libraries have already been installed, mainly for communities in Hudson and Madison, Wisconsin. The goal is their number to reach 2,500 across the U.S.