Copyright is a set of rights that protects the works of authors, artists, composers, and others from being used by other people without permission It is articulated in the United States Constitution and ensured by Title 17 of the U.S. Code. Copyright guarantees that the owner of a copyrighted work has the exclusive right to reproduce it, distribute it, perform it publicly, and prepare derivative works based upon it. According to the U.S. Constitution, copyright is not only for the protection of creators, it is also designed to "promote the progress of science and useful arts" (Article 1, Section 8, Clause 8).
Just because something is copyrighted doesn't mean you may not use it. You are not infringing on copyright if:
Not everything is copyright-able.
Libraries act as physical and not intellectual property holders. They primarily rely on Section 109, the "First Sale" doctrine, to lend and circulate materials. The term "first sale" comes from the concept that the copyright owner's exclusive right to distribute a particular copy, (such as a particular copy of a book), comes to an end when the copyright owner makes its first sale of that book.