In Susan Cooper’s The Boggart Fights Back, an obnoxious American real estate developer threatens to build an outsized luxury resort on a bucolic bit of Scottish coastline.

“ ‘Hey—seals!’ the big man called out, grinning,” Cooper writes. “ ‘That’s a huge attraction, huge! We got a real live Scottish castle and real live Scottish seals! People are gonna just love that!’ ”

“You could say William Trout is clearly a satire on Donald Trump,” says the Newbery Medal-winning author of the internationally famous, millions-selling series The Dark Is Rising.

Cooper was born in England and has long lived in the United States.

“When I started to write it, he was just a real estate developer and a television celebrity,” she says by phone from home in Massachusetts. “He hadn’t started running for office. So, to that extent, I’m not deliberately politicizing this children’s book.

“On the other hand,” she says, “he is now a political figure, and I didn’t remove the book from circulation.”

The Boggart Fights Back extends a sequence begun over 20 years ago, with The Boggart and The Boggart and the Monster. Cooper’s boggarts are fantastical creatures, shape-shifters and mischief-makers, who tricked and befriended preteens Tom Cameron and Emily Volnik in the first two books.

In The Boggart Fights Back, Tom and Emily are grown, married, and parents to twins Allie and Jay, who are visiting their grandfather in Scotland when Mr. Trout comes to town.

“The first two books were rooted in that particular place, which is wonderful,” Cooper says of Scotland. She thought to revisit the area (in fiction) after writing 2013’s Ghost Hawk, a story of the Wampanoag people, whose numbers and lands were decimated by the arrival of the Pilgrims at Plymouth Rock. “I’d just spent four or five years doing a book that was tough, so I thought it’d be nice to have some fun [back in Scotland].”

Cooper is a recipient of the American Library Association’s Margaret A. Edwards Award for significant contributions to young adult literature. Her work is consistently rooted in place, with conservation and conscientious stewardship of the land as major themes.

“The threat to the place was the idea that came,” she says of The Boggart Fights Back, “so there I was.”

With his deep pockets and bureaucratic knowhow, Trout presents a formidable threat to the pristine Scottish coast. But with a little help from their grandfather—and the impish boggarts of Castle Keep, of course—Allie and Jay will fight to defend the sanctity, history, and honor of their ancestral home.

“ ‘Gi’e a thought, Mr. Trout, to a place where no man has control’...” Cooper writes in the voice of their grandfather, Angus Cameron. “‘A place with wild things, that no man can buy, or own, or use. This place doesnae want ye, Mr. Trout. Nor all your concrete and towers and dirt, wi’ your high talk about jobs that means nothing but a way to make you money. This place wants ye to go.’ ”

“If you have strong opinions about something,” as a children’s author, Cooper says, “you have to make your passions felt. This is how kids learn and form opinions of their own. You hope that they will be reading a range of things, but it doesn’t mean you should censor your own fiction.”

Megan Labrise is a staff writer and co-host of the Fully Booked podcast.