The mainstream comedy world is dominated by left-of-center voices, but that doesn't mean conservatives don't have a voracious appetite for humor.

Just ask Michael J. Knowles, a 26-year-old history buff with a degree from Yale whose name graces the cover of the top-selling book on Amazon at the moment:

A quick glance at the table of contents suggests that the book is as humorless as its title is dry.

But flip through a few chapters and you'll quickly notice that all 266 pages — wait for it — are completely blank.

Get it? There ARE no reasons to vote for Democrats — ba dum tss!

If you find yourself LOLing, you're not alone. In March, more than 60,000 copies of the $6 paperback were sold in less than a week, making a book nearly devoid of words the top-selling book on Amazon. Should we expect anything less from the universe in 2017? Probably not.

A month later, on Monday, the book was endorsed by the most powerful of all Republicans.

Like many of Trump's tweets, the endorsement was published shortly after Knowles appeared on cable television to highlight his book's rerelease by Simon & Schuster — and to praise the president's foreign policy.

About an hour after his appearance on “Fox & Friends,” Knowles told The Washington Post, his phone “began to blow up” with text messages and notifications. Knowles said he thought he was being pranked until he checked the president's Twitter feed.

“I saw that the president not only quoted the segment, but endorsed the book,” he said. “It's a real honor to get a presidential endorsement for such important scholarship.”

He added: “I would've been more nervous had I known that the leader of the free world was watching me discuss my scholarly blank book on TV.”

Trump has credited “Fox & Friends” for his political rise.

And he is a regular viewer — as evidenced by his tweets that often follow the Fox morning show's programming.

“Fox & Friends” seems to be Trump's new favorite show, and the hosts are well aware of it. This is a place where White House aides can expect space to fully explain themselves without a flurry of follow-up questions and where the president can hear a defense of his policies and statements. In late January, the anchors jokingly told the president to flash the lights in the White House if he was watching and then showed footage of a light turning on and off on the upper floor — although they quickly explained that this was a “video effect” and that the president hadn't actually responded.
But the same message was communicated from the White House to the white couch on Tuesday morning, as the @realDonaldTrump tweeted half-a-dozen messages that seemed to directly respond to the show. (Three of the tweets were also sent from the president's formal account, @POTUS.)

Trump's Monday morning endorsement of “Reasons to Vote for Democrats” was almost immediately reflected in book sales, Knowles said. Within hours, the book had climbed hundreds of spots back into Amazon's top 100 bestsellers; it currently ranks 30th.

As for critics making light of the book-averse president endorsing a book without words, Knowles thinks they're falling for the president's savvy self-deprecation.

“This is further evidence that the president just knows what buttons to push to elicit a reaction from his political opponents,” he said. “It's so masterful.”

You may be shaking your head about all of this — but so is Knowles, who told The Post in March that he can barely believe the power of his writerly touch.

“When this book sold 100 copies, it was a funny joke,” he said. “When it sold 5,000 copies, it was a very funny joke. When it sold 50,000 copies, it made me pause and begin to think about the state of our culture.”

And what does the book's success say about the state of American culture?

“President Trump has shown us that having a good sense of humor is tremendously effective in politics and has been sorely lacking,” Knowles added. “There's an appetite for that humor, but I also think the thesis of the book is correct. I think the left has destroyed itself and its electoral viability by refusing to stand for anything.”

Knowles is an aspiring actor from Los Angeles who writes for the conservative advocacy site the Daily Wire.

As his sales skyrocketed last month, he ended up on “Fox & Friends” discussing his masterwork.

Knowles's book arrives four months after a similar book appealing to liberal sensibilities.

The title of the other side's blank book: “Why Trump Deserves Trust, Respect and Admiration.”

To date, the $6.09 book on Trump has sold more than 20,000 copies and been ranked as high as No. 33 on the Amazon bestseller list. The book has also generated more than 592 customers reviews with an average of 4.4 out of 5 stars.

On Amazon, customers are told they should feel free to use the book's 206 pages for notes.

David King, the book's 32-year-old British creator, claims (only somewhat playfully) that his conservative counterpart ripped off the idea for a blank book from him and has even used similar language to describe his tone (i.e. “exhaustively researched”).

“It's a rehash of my book really and not unlike what the Republicans are trying to do with Obamacare,” he said in March, referring to Knowles's work. “The one difference being that mine speaks the truth.”

King said he was transfixed by Trump's rapid rise from political laughingstock to U.S. president. He was sitting on the London underground when the idea for his book struck him several weeks after Trump's election.

“I did further research to figure out if he was worthy of respect after the election, but I genuinely couldn't find any evidence that he is,” he said.

“The book is very amusing and sums up a lot of the sentiment and the feeling that a lot of people in America have about Trump,” he said. “You can see that in some of the customer reviews — they're absolutely hysterical.”

“A well-researched, well-written and 100% accurate catalog of Mr. Trump's greatest strengths,” a customer named Michael Coles wrote. “People have read it, and let me tell you, they love it. It's the best book. It's going to be yuuuuuge. Bigly.”

“Very, very, yugely poor translation from original Russian,” Nancy Gormezano added. “And that's Putin it mildly. Maybe kindle version be better?”

In response to Trump's vulgar language, King said he's donating 50 percent of the book's sales to the women's rights charity Equality Now.

Knowles claims his book is no copycat — he says he'd never heard of King's book when he published his own blank book. Both men said they initially thought they had stumbled upon an original idea when they came up with their book ideas, but Bob Mecoy, a New York literary agent, said that's not the case.

The genre goes back decades, he said, noting that blank books have been a recurring meme that has manifested in numerous genres, including pop psychology and politics.

“There is a great giggle tradition of nothing being great satire,” Mecoy said. “There is always someone who realizes that all they need to do is put a cover on it and it will sell.”

“They go from coffee table book to coaster pretty quickly,” he added.

Right now — as far as jokes are concerned — Knowles is producing more laughs than his liberal competitor.

“Why Trump Deserves Trust” has fallen all the way to No. 7,393 on Amazon's bestseller list.

Jokes aside, Knowles has an explanation for this. He said that not only do conservatives have a better sense of humor than liberals, but they're “so much better at the Internet.” Shut out of the mainstream media, he said, conservatives have created their own online ecosystem where information and enthusiasm travel rapidly.

“Comedy Central doesn't allow conservatives within 200 yards of their shows, but my gag book is trouncing Trevor Noah's book,” he said. “I've found that the humor that's been coming out of the right in the last few years has been tremendously more effective and had a wider reach than the mainstream liberal outlets.”

What's next for the fledgling author?

“I'm working on my multivolume, Caro-esque history of Hillary Clinton's presidency,” he said. “In fact, I finished it just now while we've been on the phone.”

This post, originally published March 15, has been updated following President Trump's endorsement.