Todd Heisler/The New York Times

As the rain poured down over Lower Manhattan on a recent weeknight, a patchwork of umbrellas and tarps in the northeast corner of Zuccotti Park was preventing something very precious from getting wet: the books of Occupy Wall Street’s self-run People’s Library.

While the library’s most popular titles are progressive tomes on politics and the economy, donated books are never rejected, even if they seem at odds with the ideology behind the protest.

“We’ve gotten books by Ann Coulter and Milton Friedman,” said Zachary Loeb, one of the volunteer librarians. “But my favorite was a how-to magic book, written in French.”

The People’s Library started a few days after Sept. 17, the day that the Occupy Wall Street protest began. People were leaving books they had finished on one of the benches in the park, and as a pile amassed, organization-minded protesters started putting them in boxes, then arranging them by genre.

All of the books have all been donated — by individuals, publishers and even authors — simply so that protesters have something to read. Over the past four weeks, the collection has steadily grown to about 3,000.

“When there’s nice weather, when people can hang out here, there’s a lot of reading going on,” said William Scott, an English professor from the University of Pittsburgh and one of the librarians at the People’s Library.

As the collection grew, protesters set up tables and began helping people find specific titles among the boxes. Then, with the help of Radical Reference, a volunteer collective of librarians who lend support to activist causes, they built a catalog and started entering the books that were coming in, either by scanning their bar codes with a smartphone or manually typing in their International Standard Book Numbers. While the catalog does not indicate whether a book has been checked out, it does track the titles that are being donated, serving as an “interesting archival document,” according to Mr. Loeb.

The library runs on the honor system: anyone can take out a book, and there are no official due dates or library cards. But it is more than just a glorified book swap. About a dozen core librarians take turns fielding inquiries at the reference desk, recommending books when requested titles aren’t available, and logging new donations into the library’s catalog, which can be searched online at peopleslibrary.wordpress.com/.

In addition, the librarians are trying to set up a Wi-Fi network so that people can use the Internet without charge, just as they can at a public library.

“It goes hand in hand with the movement,” Professor Scott said, “which in part, is about expanding access to education.”

The library’s collection comprises material as varied as philosophy, literature and even a constantly growing archive of poems and plays written by protesters themselves. The librarians have established a noncirculating section to ensure the availability of the most sought-after titles, which include “A People’s History of the United States” by Howard Zinn, “The Shock Doctrine” by Naomi Klein, and “Nickel and Dimed” by Barbara Ehrenreich.

Professor Scott and Mr. Loeb said that the publisher Knopf donated 50 books to the People’s Library last Wednesday and that they had also received a box of 20 copies of the Scrabble-like word game Bananagrams from an anonymous donor. In the past few weeks, authors like Ms. Klein and Chris Hedges, a former reporter for The New York Times, have donated multiple copies of their own books after coming to speak at Zuccotti Park.

But most of the donations are small and come from individuals, according to Mr. Loeb. On Wednesday night, a young man ducked into the makeshift covering protecting the People’s Library and offered three books, including the much coveted “Nickel and Dimed.”

According to Mr. Loeb, passers-by are often surprised when they see the library, which is situated at the high-profile corner of Broadway and Liberty Street, and come in to ask questions about it.

“When people think of a library, they think of organization and they think of people saying ‘shhh,’ ” Mr. Loeb said as a small marching band played in another section of the park.

“All these things that people don’t think this scrappy encampment would have.”