Since long before she moved to Concord six years ago, Mary McEvoy-Barrett has taken a daily walk through Rollins Park.

It was part of why she and her husband, Ray Barrett, picked their house in the South End.

“There were too many hills in Dunbarton,” according to Ray.

The couple are, by their own description, a classic “farm boy, city girl” story. Ray is from Hudson, Mary from Nashua; they raised their family in Dunbarton before downsizing to Concord.

Mary knows every bend, every fork in Rollins Park’s paths. She notices how many people come and go every day, how many kids are on the playground, how many books are in the Little Free Library.

Little Free Libraries are a popular sight in Concord and increasingly across the country. Often resembling mailboxes or birdhouses, anyone can leave a book or take a book at their leisure, no due date necessary.

It was on a walk through Rollins in August when Mary saw that the Little Free Library — a 2016 Eagle Scout project by Cole Beachemin, according to its plaque — was broken. The sandy-brown saltbox has a split riding up its side and it hung off the back of its bearings, like it had taken a good punch.

She realized she couldn’t just leave it like that. This little free library, not only because it’s in her favorite park, is a special one because it helps Mary’s sister’s memory alive.

Ellen McEvoy, who died in May, was a lifelong bookworm: She had long been a “book lady” at the St. Joseph’s Home for Children in Minneapolis, and she traveled across the country and New Hampshire, after moving back here, visiting libraries, documenting each one in her blog, “Every Library I Can.”

“She read everything,” Mary said. “There was nothing she wouldn’t pick up and read.”

Ellen, who lived in Concord when she died, left behind an enormous collection of books — Shakespeare, sports, mystery, even books about death.

Every few days, Mary harvests a few from the boxes and boxes in her home. She marks them with a stamp she had made in Ellen’s honor, slides them into a tote bag and, on her walk through Rollins, deposits them in the Little Free Library, tucking them in beside children’s books and puzzles.

The grass in front of the Little Free Library in Rollins is worn down to dirt. And whenever Mary passes by again, Ellen’s books have been checked out.

“Sometimes I put one in there and think, ‘Nobody will be into this,’ ” Mary said, laughing to herself. “And every time, when I come back, they’re all gone.”

Mary is a lover of traditional libraries, too. But slowly spreading pieces of Ellen’s collection through the South End just feels right.

She likes that, when someone “checks out” one of Ellen’s books, or any book inside, they get to keep it. It’s theirs for as long as they like, to add to their own collection or pass on to the next. What people leave and take from the library, Mary said, is also a small pulse of the neighborhood.

“You get a little insight into the people around you,” she said.

It’s also just a way to get rid of the books, she added with a laugh.

Mary doesn’t just leave Ellen’s books in Rollins. She keeps a bag full in the trunk of her Subaru.

Sometimes, when she passes by a little free library on the road, she’ll pull over and leave one.

When she found the library in Rollins busted, she was upset. It wasn’t the first time this one, or others in parks across the city, had been damaged.

Ray carefully removed the little brown saltbox from its perch and the couple took it home, determined to repair it.

“Like any project, it became twice as complicated,” Ray said. It needed a new bottom and a coat of paint. But within a few days, the couple returned the library to its perch and added a few new books for good measure.

Mary and Ray aren’t the first people to whisk the little library away for repairs. First, the plastic window on the door — the one you peer in to scope out what’s inside — was smashed. After that was fixed, someone ripped the door off entirely.

At some point, the couple knows that they, or another Rollins devotee, will have to fix it up again. They’re happy to do it.

“We’ll just keep putting back it together,” Ray said, “until someday we have to build a new one.”

Catherine McLaughlin can be reached at cmclaughlin@cmonitor.com.