(AP Photo/Brad Barket, File) (AP Photo/Brad Barket)

Tuesday night, when Jon Stewart announced that he would be stepping down from “The Daily Show,” millennials across the country were shocked and saddened.

But book publicists were crushed.

In an increasingly fractured market, “The Daily Show” has been a singular platform for authors to promote their books.

New York Times Book Review editor Pamela Paul called it last night on Twitter:

“Getting an author booked on ‘The Daily Show’ was often the Holy Grail for book publicists,” says Kate Lloyd, Scribner’s associate director of publicity. Her authors loved Stewart, she says, because “his audience is made up of smart, book-buying readers who respond to the thoughtful treatment and authentic passion he customarily expresses for the books he features.”

Oprah used to tower over the world of publishing, but her new Book Club 2.0 doesn’t seem to create nearly the cultural buzz of her old TV book club. (This week, Oprah picked Cynthia Bond’s “Ruby.”)

Elizabeth Riley, senior director of publicity at W.W. Norton, calls Stewart “the intellectual author’s Oprah.” Riley says being on “The Daily Show” is “the dream interview every serious nonfiction writer mentions during that first strategy meeting. And there’s a reason for this. We just had Sarah Chayes on the show last week for ‘Thieves of State,’ and sales leapt up significantly from the week before. What other show could do that for a book on global corruption?”

​Indeed, Stewart’s eclectic taste often provided a boost to titles that wouldn’t ordinarily receive a lot of media attention. For instance, after his interview with David Mitchell, who translated Naoki Higashida’s memoir from the Japanese, sales of “The Reason I Jump” exploded, and the book became a major bestseller, according to Sally Marvin, director of publicity at Random House, Spiegel & Grau and the Dial Press. She calls Stewart’s decision “a huge loss.”

Publishers love to sell more books, of course, but Paul Bogaards, executive vice president of Knopf Doubleday, notes that Stewart’s influence has been more significant than the raw sales numbers suggest. “Publishers don’t have a lot of substantive broadcast booking options for authors,” he says. “The value of Jon Stewart welcoming writers on his show, giving them a platform and making them a part of the conversational mix was quantifiable in this sense: He elevated the work of authors, made books relevant to a younger demographic. And that demographic remains challenging for publishers to reach, at least en masse.”

Kathleen Schmidt, publicity director at Weinstein Books, notes that the timing of Stewart’s departure is particularly bad. “Heading into what will surely be an interesting election season full of political books, publishers are losing a very important piece to the publicity puzzle,” she says. “For certain kinds of books, ‘The Daily Show’ has been an invaluable vehicle for promotion. Books about politics, public policy, biographies, that otherwise would be difficult to promote on a network morning show found their audience through Jon Stewart.”

Stewart had an almost unique ability to push books into the ongoing coverage of current news. Kathleen Zrelak, director of publicity at Goldberg McDuffie Communications, cites Canadian journalist Robyn Doolittle, who broke the Rob Ford scandal. “She and her book ‘Crazy Town’ became part of the conversation, discussed in the news cycle and on social media in the days and weeks following her interview on ‘The Daily Show,’ ” Zrelak says.

Zrelak will particularly miss Stewart’s willingness to highlight smaller titles. “You don’t need to be a household name to get on the show,” she says, “just someone who has a book that advances an argument, a journalist who exposes corruption, a whistleblower, an academic with a fresh thesis.”

Deb Seager, director of publicity at Grove/Atlantic, fondly remembers the time Stewart interviewed Sam Sheridan about “A Fighter’s Heart: One Man’s Journey Through the World of Fighting.” Sheridan’s appearance on “The Daily Show” took that book “to the next level,” she says.

But maybe we should just be grateful for what we got over the past 16 years. “We were probably lucky to have the show with Stewart at its helm as long as we did,” says Peter Miller, director of publicity at Liveright. “When they started to book authors — the wonkier and untelegenic the better — it was an unexpected gift to publishers of serious nonfiction, like a bizarro C-SPAN. This is probably a sad, sad day for university presses.”