For a genre that’s so popular among readers of all ages, young-adult (YA) lit is surprisingly young: The term was only coined in the 1960s, introducing an official way to describe books aimed at kids 12 to 18. In the relatively short time since, change has come — again and again. At its inception, there was a goal of realism that’s remained relatively consistent, but along the way, there have been so-called problem novels, pastel-covered paperback romances and fantastical fiction.

“That’s a pretty fast evolution,” says Teri S. Lesesne, a professor of library science at Sam Houston State University. “I think it far surpasses what we see in adult land.”

Here’s a look at the evolution of YA lit through nine books that span 50 years.

"The Outsiders," S.E. Hinton (1967)

Hinton was a teenager herself when she wrote this timeless, gritty tale of class conflict and parental abandonment. It’s widely considered the first real YA novel. “The appearance of ‘The Outsiders’ was both a turning point and a paradigm shift,” says Michelle Ann Abate, a professor of literature for children and young adults at Ohio State University. “What Hinton was trying to do was provide books for young readers that talked openly and honestly about real issues that impacted their lives: socioeconomic class differences, bullying, peer pressure.” The novel, still studied in classrooms today, ushered in an era of realism for YA lit, right down to the language young readers used.

"Go Ask Alice," Beatrice Sparks (1971)

There was realism done well and then there was the spate of “problem novels” that dotted the 1970s — formulaic takes on a single issue, such as eating disorders, bullying or, in the case of “Go Ask Alice,” teen drug addiction. “It was like the after-school special on TV — ‘I have a problem and in an hour I’ve solved it and everybody’s happy,’ ” Lesesne says. The focus was always on a single issue, not artful storytelling or fleshed-out characters. Although critics mocked problem novels, many — such as “Go Ask Alice” — were popular among teens, who were perfectly happy to read about the troubles plaguing other people.

"Forever," Judy Blume (1975)

For a long time, sex wasn’t mentioned in YA novels — and if it was, the tone was preachy at best: Protagonist gets pregnant and must drop out of school and get married, or suffers some terrible karmic payback. The story lines centered on the consequences, not the act itself — or the feelings that were or weren’t involved. That changed with “Forever,” which saw a high school couple fully explore their sexual desires. The female protagonist even went to Planned Parenthood for the pill. Birth control choices for young women — a revelation! Blume’s candor encouraged other writers to take a more liberal, positive approach to sex in their work, too.

"Sweet Valley High" series, Francine Pascal (1984)

The 1980s brought genre fiction, mostly romance and horror series with endless volumes. “Sweet Valley High” was one of the most beloved. After debuting in 1984, what was meant to be a six-book series turned into nearly 150. In 1985, a “Sweet Valley” Super Edition, “Perfect Summer,” became the first young adult novel to land on the New York Times paperback bestseller list. It’s easy to dismiss the pastel-covered series of this era as superficial fluff, but the books signaled a desire for escapism — and a turn away from the hard-edge problems that dominated the earlier YA market.

"Harry Potter" series, J.K. Rowling (1998)

It was something like magic when “Harry Potter and the Sorcerer’s Stone” was published in the United States in 1998: The beloved boy wizard cast a spell over readers of all ages, conjuring a spectacular publishing phenomenon. Rowling’s seven-book series is one of the reasons the New York Times created a children’s bestsellers list; with so many “Potter” books hanging out on the adult list, there wasn’t enough room for other deserving titles. The series kick-started a YA novel-to-blockbuster-movie boom and waved in an era of speculative fiction, while also making publishing events a thing: Think midnight releases and costume-heavy bookstore gatherings.

"Twilight" series, Stephenie Meyer (2005)

After the unprecedented success of “Harry Potter,” it was only a matter of time before readers were sucked into the next YA frenzy. In 2005, it arrived: “Twilight,” the vampire love story by debut author Stephenie Meyer. The four-volume saga signaled another trend — the paranormal romance — and, like the “Potter” books, saw huge success both in print and on the big screen. “Twilight” inspired dozens of knockoffs, as well as fan fiction that became popular in its own right. It’s also the reason the love triangle came to play a major role in YA lit in the following years.

"The Hunger Games" trilogy, Suzanne Collins (2008)

“The Hunger Games,” along with “Harry Potter” and “Twilight,” completes the trilogy of series that overhauled recent YA lit. Suzanne Collins’s tale of young tributaries competing to the death in the post-apocalyptic nation of Panem explored social and political themes and was lauded for its strong, complex female lead (whose worth was not tied to a romantic interest — though she had two). The series inspired an influx in dystopian fiction. “YA is just a real reflection of what’s going on in society,” Lesesne says. “Even the dystopia.”

"We Are Okay," Nina LaCour (2017)

YA lit starring LGBTQ characters isn’t new, but the options haven’t always been good — or plentiful. A decade ago, the story line might have centered on the hardships of being a gay teen. But “now it’s to the point where you have an LGBTQ character, and sexual orientation has nothing to do with the story,” Lesesne says. Case in point: “We Are Okay,” which won the 2018 Printz Award. The book examines grief, friendship and romance — including the complicated relationship between the two female protagonists.

"The Hate U Give," Angie Thomas (2017)

YA fiction has long had a diversity problem, in part because of a white-dominated publishing industry. But there’s reason to be optimistic, Lesesne says: “We’re seeing more characters of color. Not enough, but we’re starting to see it.” A recent, high-profile example is Angie Thomas’s “The Hate U Give,” inspired by the Black Lives Matter movement. “THUG,” which was turned into a movie this year, examines police brutality through the eyes of a black teen who lost two of her childhood friends to gun violence, and its success indicates movement toward more African American YA authors and characters. Let’s hope, anyway, because what’s the point of YA if not to showcase the wide range of all teens’ experiences?

Angela Haupt  is a writer and editor based in the District.