NEW YORK — The country’s hottest book isn’t a hit because of Oprah Winfrey or Donald Trump. It’s all because of a laughing Scottish grandmother.

Thanks to a viral video of Janice Clark reading Craig Smith’s “The Wonky Donkey” to her baby grandson, and her breathless amusement over lines such as “He was a honky-tonky winky wonky donkey,” the 2009 picture book about a three-legged, one-eyed donkey has sold more than 100,000 copies in the United States this fall, much of that in the past week. According to NPD BookScan, which tracks around 85 percent of the print market, “Wonky Donkey” topped all releases with more than 90,000 copies sold last week, beating out Bob Woodward’s “Fear” and Rachel Hollis’ “Girl, Wash Your Face,” among others.

“You can’t ask for a better endorsement of your creation than when the person reading your book is having a better time than the child being read to. Janice’s infectious laughter was an absolute delight!” wrote Smith, a New Zealand-based musician and author, in a recent email. “Remember, this viral sensation came about because a grandmother read a BOOK to her grandson, albeit a very special grandmother.”

“The Wonky Donkey,” featuring illustrations by Katz Cowley, had already sold hundreds of thousands of copies in New Zealand and Australia, where Clark, a native of Scotland, now lives. But until recently it had a much smaller audience in the United States. According to Scholastic, the book had sold about 75,000 copies and was out of print before the video caught on last month.

Scholastic said it has ordered 600,000 copies.