It’s fall, which means the best-seller lists are brimming with new titles — this week, 12 of them, including “The Giver of Stars,” Jojo Moyes’s novel about Depression-era librarians in Kentucky; “Deep State,” James Stewart’s look at how the F.B.I. investigated Hillary Clinton and Donald Trump; “Tough Love,” Susan Rice’s memoir about her life and her time as national security adviser; and “Ninth House,” Leigh Bardugo’s first adult novel, about a young woman deeply enmeshed in Yale’s secret societies. “Y.A. fiction tends to have a finite quality,” Bardugo told The Times recently. “You’re looking toward a goal — prom or graduation or revolution — and we leave these characters after a moment of tremendous transformation.” But in “Ninth House,” which is the first in a series, “the challenges faced by my heroine are different and don’t stop at one particular point,” she said.

“This story was going to begin like all the best stories. With a school bus falling from the sky,” begins Jason Reynolds’s new novel, “Look Both Ways: A Tale Told in Ten Blocks.” The book, which enters the middle-grade hardcover list this week at No. 2, follows a group of kids — “in the same school, in the same classrooms, but all of whom have very different journeys” as they walk home from school each afternoon.

“I am fascinated by moments of freedom in children’s lives,” Reynolds said. But he thinks too many writers create that freedom in artificial ways — by killing off parents, or stranding boys and girls in strange places. Neither tactic appeals to him. “Most of my books, you notice that there is always the adult component,” he said. “Because I think that’s important in children’s lives, and healthy adults and flawed adults are very real.”

It dawned on Reynolds that many kids — specifically, the ones who walk to and from school — have small blocks of time every day that are completely free from adult supervision. “It’s in this time that they get to learn about the world on their own, for better or for worse,” he said.