While au fait literary types around town await the buzzed-about new novels from Jonathan Franzen and Nicole Krauss, other former English majors have spent the summer trying to get hold of “Mockingjay,” the third book in Suzanne Collins’s dystopian trilogy, so intensely under wraps that not even reviewers have been allowed a glimpse before its airtight Aug. 24 release. What fate will befall our heroine, Katniss Everdeen? My fellow book club members and I are desperate to know. When will the Capitol fall? And how can Collins possibly top the first two installments, “The Hunger Games” and “Catching Fire”?

Oh, did I mention? “Mockingjay” is for teenagers. I am well into my 30s.

But I am not embarrassed by my, shall we say, immature taste in literature. And I wasn’t much concerned when, barreling through “The Hunger Games” at the hospital after giving birth to my third child, I hardly noticed whether he ate or slept. When will the rebellion begin, I wanted to know. Which suitor will Katniss choose? Nor am I alone. According to David Levithan, editorial director at Scholastic, Collins’s publisher, roughly half of the “Hunger Games” fans on Facebook are full-fledged adults. “The Harry Potter generation has grown up,” he told me.

It isn’t just the kids who graduated with the Hogwarts crowd who are tuning in. After all, the historian Amanda Foreman, a 42-year-old mother of five and author of “Georgiana: Duchess of Devonshire,” was honeymooning when she first read Harry. When I asked Foreman about her young adult reading habit, she could hardly contain her enthusiasm. I must, she urged, read Susan Cooper (“incredibly clever”), Eoin Colfer (“a brilliant author”), Rick Riordan (“really, really, really good”). I must! “A lot of adult literature is all art and no heart,” Foreman, who is currently working on a book about British involvement in the American Civil War, said. “But good Y.A. is like good television. There’s a freshness there; it’s engaging. Y.A. authors aren’t writing about middle-aged anomie or ­disappointed people.”

That may be, in part, why so many middle-aged readers like them. (“They’re also easier to read, and people are tired,” Lizzie Skurnick, author of the anthology “Shelf Discovery: The Teen Classics We Never Stopped Reading,” suggested. “I’m sure I’ll get in trouble for saying that.”) But big type and short, plot-driven chapters aside, the erosion of age-­determined book categories, initiated by Harry Potter, has been hastened along by an influx of crossover authors like Stephenie Meyer and interlopers like Sherman Alexie, James Patterson, Francine Prose, Carl Hiaasen and John Grisham, to name just a few stars from across the spectrum of adult fiction who have turned to writing Y.A. According to surveys by the Codex Group, a consultant to the publishing industry, 47 percent of 18- to 24-year-old women and 24 percent of same-aged men say most of the books they buy are classified as young adult. The percentage of female Y.A. fans between the ages of 25 and 44 has nearly doubled in the past four years. Today, nearly one in five 35- to 44-year-olds say they most frequently buy Y.A. books. For themselves.