Juvenile literature of any kind didn't exist until the 1700s, when authors began writing moral and educational tales and poems. This literature was generally steeped in a Christian worldview, though it tended to be so didactic and unrealistic that it is unlikely that many Christian parents would choose to share it with their children today. It wasn't until the early 1900s that children's literature was born in the sense that we know it today--stories written for entertainment and delight. YA literature, however, wasn't born until the World War II era, when teenagers were first recognized as a distinct social grouping. And it was also during World War II, in 1942, that YA literature was born with the very first novel written just for teens: Seventeenth Summer, by Maureen Daly.
If this is the case, then what did teens read before 1942? Throughout history, dating from ancient times to the 20th century, teens read what adults read: Homer's epics, Chaucer, The Count of Monte Christo, Little Women, The Hobbit, and so on. Some of these novels, of course, featured young people, such as the four sisters in Little Women. By and large, though, teens were part of the adult world and entertained themselves with adult literature. Exceptions to this may be the few formula-fiction series available in the early 20th century, which featured young adults--for example, the Nancy Drew series and the Hardy Boys series. These, however, were not marketed specifically to teens.
After Seventeenth Summer was published, only a few teen-oriented books were notable for their literary quality until the 1960s. These included the still-popular Johnny Tremain and Catcher in the Rye. In 1967, though, young adult literature began its first golden age with the publication of S.E. Hinton's classic, The Outsiders. After her breakthrough (a success story notable for the fact that she was a teen herself when The Outsiders was published), more authors stepped up to produce some of the most memorable novels in the YA genre: Judy Blume, Lois Duncan, Robert Cormier, Paul Zindel, Katherine Paterson, William Armstrong, and more. This period, too, saw the rise of the "problem" novel, where the plot focused on a single issue, such as death or drugs. Most of these fell by the wayside over time, as they became more and more formulaic. But the most popular authors of that first golden age are still read today.
Still, as a genre in its own right, YA literature didn't really take off until the early 2000s, when it virtually leaped into the spotlight on the heels of the Harry Potter phenomenon. Since then, more and more authors have presented the teen world with their creations, particularly blockbuster series like Twilight and The Hunger Games. YA literature has become so complex, enjoyable, and sophisticated in recent years, in fact, that many adults are now reading the same novels that teens enjoy. Two of the most popular types of novels in the YA genre today are dystopian and paranormal, but YA spans the gamut, offering all types of stories to meet every interest.
The challenge for cautious parents today, it seems, is not finding good stories for their teens to read, but finding stories that do not betray their values and beliefs. YA has grown up, now often seeming more firmly adult in its content and themes than oriented to young people who are still growing and impressionable. Yet, despite its mature content, YA literature has greatly improved in general quality over the past couple of decades--a welcome change that all parents can celebrate.