FOR MANY years, Gene Luen Yang led something of a double life. By day, he was a mild-mannered teacher, walking the halls of his Bay Area high school as a tall and bespectacled expert in computer science. But by night, he would embark on adventures with a separate sense of mission, losing himself in tales of superheroism and dual identity. And if his greatest power was literary imagination, his second-greatest involved stellar feats of time management. Yes, after dark, Mr. Yang became…

A comic-book creator.

Ever since, his list of achievements has grown as imposing as a tall building leapt in a single-bound volume — bestseller to bestseller, along the way authoring two graphic novels that have been shortlisted for the National Book Award.

As a product of all his accomplishments as author and educator, Yang is being announced today as the new national ambassador for Young People’s Literature. The Center for the Book in the Library of Congress, the Children’s Book Council and Every Child a Reader will inaugurate Yang on Thursday in Washington in a free event open to the public.

Thrilled and humbled by the honor, Yang embraces this opportunity as a welcome part of a professional progression. “I’m really attached to furthering the integration of the book and comic-book worlds,” says Yang, whose current projects include writing a YA book series and DC Comics’s Superman. “This is the next logical step.”

Yang is accustomed to logical steps that also represent pioneering firsts. A decade ago, his cross-cultural masterwork “American Born Chinese” became the first graphic novel ever to be named a National Book Award finalist — a feat he repeated more recently with his sweeping Boxer Rebellion epic, “Boxers & Saints.” Now Yang becomes the first of the five Young People’s Literature national ambassadors to be a graphic novelist. (The literary figures previously appointed to the two-year ambassadorship have been Jon Scieszka, Katherine Paterson, Walter Dean Myers and Kate DiCamillo.)

This literary ambassador program was created in 2008 “to raise national awareness of the importance of young people’s literature as it relates to literacy, education and the betterment of the lives of young people,” according to its organizing bodies. With that in mind, Yang tells The Post’s Comic Riffs that “one of the things I’m supposed to do as ambassador is promote great books, and because I’m from the world of graphic novels … I have to give them a little bit of an extra push.”

Yang is accustomed to coming to Washington and winning over fans of graphic novels in a Library of Congress setting. In the summer of 2014, the author-educator memorably spoke at a National Book Festival kickoff event, sharing the stage with fellow speakers E.L. Doctorow, Nina Khruscheva and Kai Bird, as well as festival board co-chair David Rubenstein and Librarian of Congress James H. Billington. Yang drew some of the night’s loudest cheers — and highest praise — by talking passionately from the pulpit of comics and visual storytelling. He spoke not only of the need to promote culturally diverse literature, but also of the courage required by authors to give themselves permission to write about cultures outside of their own.

“We in the book community are in the middle of a sustained conversation about diversity,” Yang said to the Jefferson Building’s well-heeled assemblage that evening. “We talk about our need for diverse books with diverse characters written by diverse writers. I wholeheartedly agree. But I have noticed an undercurrent of fear in many of our discussions. We’re afraid of writing characters different from ourselves because we’re afraid of getting it wrong. We’re afraid of what the Internet might say.

“This fear can be a good thing if it drives us to do our homework, to be meticulous in our cultural research,” Yang continued. “But this fear crosses the line when we become so intimidated that we quietly make choices against stepping out of our own identities.”

Immediately after that speech, Yang told me it also functioned as a pep talk for himself as a writer. That’s crucial because the notion of identity — both discovered and secreted — runs through most of his work, including 2014’s “The Shadow Hero,” which creates a new narrative for a ’40s comics character (the Green Turtle) who was perhaps the first Asian American superhero.

Yang, who is in his early 40s, was raised in the Bay Area as the son of immigrants. Themes of being a Chinese American, as well as a Christian, recur in his work. He also often explores the idea of outsider status — one that dovetails nicely with being a comics fan, he has noted, because the comic-book industry itself was founded largely during the World War II era by Jewish Americans who felt like outsiders.

Yang began drawing comics in fifth grade, and his rise as a cartoonist began two decades ago when he received the Xeric grant for his self-published “Gordon Yamamoto and the King of the Geeks.” His true breakthrough came nearly a decade later with “American Born Chinese,” in which stereotypes and senses of multiple identities are brilliantly explored. That book, which has sold more than a half-million copies and is a classroom staple, is the only graphic novel to win the American Library Association’s Printz Award.

Yang himself has long been a classroom staple, as well. After majoring in computer science at the University of California Berkeley, he tried being a computer engineer for a stint, only to realize that his true calling at the time was teaching. For 17 years, until last June, he taught — “mostly computers, some art and a little math” — at Bishop O’Dowd High School in Oakland, before deciding to devote more time to his thriving comics career.

So this national ambassadorship not only comes along at an ideal time, but also meets two of the cartoonist’s goals. First, Yang — who has four children of his own, but missed a stimulating classroom environment — gains a post that feeds his desire to educate.

“I still love being a teacher, and a classroom is something I want to have again,” says Yang, whose recent YA series is the tech-friendly “Secret Coders,” as well as “Avatar: The Last Airbender.” “For years, I would make comics at night and then teach during the day, and those two kinds of energy were a really nice balance for me. … When I was sick of people, I would draw. And when I was sick of being by myself, I would be in the classroom.”

The ambassador’s post also provides Yang with a platform for promoting reading, including graphic novels, with an emphasis on technology and STEM goals. He says his focus, reduced to three words, is simply Reading Without Walls. “Walls are only a big thing if you’ve never crossed them or scaled them,” he tells Comic Riffs. “There are a lot of walls between cultures that reading can help bridge; reading is a way to get to know people on a deeper level. … And we’re also talking about ways we can use technology to engage kids with reading, because the technology [we’re looking at] is so new.”

Technology can also support the strengths of a visual medium. “The fact that graphic novels have gained such a wider acceptance … is maybe an acknowledgment that our current generation of kids really responds to visual forms of communication. They’re used to seeing multimedia information.”

Such thinking surely made the author an attractive candidate for the Young Literature post. “Gene Yang continues to prove himself as a pathfinder for publishing, for comics, and for literature in our changing times,” says Mark Siegel, editorial director at Yang’s home imprint, MacMillan’s First Second Books. “This is another great honor he has earned, and another first for graphic novels as a form — a vital, timely, flourishing form of human expression. Gene is exceptionally gifted.”

And at the center of those gifts is Yang’s eagerness to push past boundaries in order to seek new ideas — and then return with inspiring word of each exciting discovery and innovation.

“After all, our job as writers is to step out of ourselves,” Yang said in his National Book Festival speech, “and to encourage our readers to do the same.”

Literature for young readers, in other words, couldn’t have a better emissary.