Take a book, leave a book. Little Free Libraries are popping up around Philly.

Every week or so, Marty Shively walks from home into Bristol Township's Silver Lake Nature Center. She nears the butterfly garden and then stops in front of a little box.

It's a library.

She pulls open the squat double doors that glide over the black-and-white piano keys she painstakingly painted on this repurposed kitchen cabinet three years ago. She studies the titles in the library, a four-by-two-foot box she and a friend assembled and painted to resemble a piano.

She recognizes some books; others are new. Some days, the little box is stuffed. On other days, amid empty space, hardbacks and paperbacks have fallen against each other, like dominoes frozen in mid-topple.

Good, she says to herself. People come here. People like this place. 

Shively's Little Free Library, at 1306 Bath Rd., is one of about 900 such libraries registered in Pennsylvania and among 75,000 across the world.

Little Free Library, a nonprofit founded in 2009, has been touted as a growing movement to expand enthusiasm for literacy and community outreach. The organization neatly sums up its mission in six words: "Take a book, leave a book." Free.

"I can go through periods where I can't even put a book in because it's so stuffed," said Shively, a retired music therapist who started the library, then in Levittown, with her longtime friend Renee Flager, formerly a children's librarian.

Although each library has its own distinctive features, all Little Free Libraries take the form of a box, often not unlike a large birdhouse, filled with books for people of all ages and propped atop a post stuck in the ground. They appear in all colors, shapes, and materials — weatherproofing is wise — and some also sport thoughtful bonuses, like dog biscuits, and tricked-out features, like motion-sensor lights. The libraries pop up wherever their creators, officially referred to as stewards, choose to place them, often in their own neighborhoods.

There are no library cards, no late fees, and no opening or closing hours. They're the furthest thing from a traditional library. And that's part of their charm.

Little Free Libraries don't try to compete with brick-and-mortar libraries, replete with thousands of books, CDs, audio books and banks of computers. The tiny kiosks are inviting in their own way.

Chris Swisher, a part-time reference desk librarian at the Tredyffrin Public Library, started a Little Free Library on Lenoir Avenue in Wayne two years ago, after his wife gave him a Little Free Library kit for Christmas.

"It thrills me when I see people stop and take a book or put in a book," he said.

Megan Patterson passes Swisher's library several times a day when she walks with her dog and 1-year-old daughter, Edie.

"We'll peek in there from time to time," she said. "I grabbed things for the baby. I got an infant massage book out of there one day."

There are dozens of Little Free Libraries in Philadelphia and its suburbs. Wayne alone boasts seven, each with its own unique character and steward.

The myriad stewards in the region include Laura Dixon Hartshorn, a captain with the Chester Township Police Department; Cathy Pritchard, a mystery and romance novelist in Narberth with a day job as a corporate legal assistant; and Mike Vaughan, the owner of Riverbend Cycles, a bicycle shop along the Schuylkill River Trail in Conshohocken.

They each have their own reasons for starting their libraries.

Hartshorn saw it as a way to build community relations for the police department. Pritchard just had too many books and decided she needed to give some away. And Vaughan, a voracious reader whose bicycle shop includes a cafe and patio, thought he'd give customers some reading material after they'd hopped off their bikes to take a break mid-ride.

"We get a lot of excitement out of it," said Vaughan, who started the library with one of his customers. His library, at 1 Station Ave., caters mostly to adults and offers a selection of historical fiction and biographies, although it once held a book about the history of the pencil.

Pritchard tries to switch up the contents of her library with themes. There was a Halloween theme last month, she said, and in April, for Earth Day, she placed some nature-themed titles to mark the occasion, as did Shively, of Bristol Township.

"It starts to take on a life of its own after a while," said Pritchard, who painted her library sage green. "It's not just me putting the books in."

Hartshorn, of the Chester Township police, has had to refill the department's library three times since it was staked into the ground outside police headquarters, 1840 Harris St., this year. Among its offerings are an array of children's books that officers bring in from home when their kids outgrow them.

"The fact we've had to refill it three times tells me people are taking advantage of it," Hartshorn said. "Nobody's going to steal a book. If they're taking a book, they want to read it to the kids."

The inspiration for Little Free Libraries came from Todd Bol, a Minnesota native who built the first one in Hudson, Wis., in 2009 as homage to his mother, a fellow teacher and book-lover. The concept took off and spread worldwide, with libraries in all 50 states and 88 other countries.

Bol died last month of pancreatic cancer at age 62, bringing a measure of sadness even to those who never met him but felt a connection through their Little Free Libraries.

"It was a great idea," said Hartshorn. "And that's even more of a reason to continue his legacy."