She had cardiovascular disease, said her husband, Leonard S. Marcus, a historian and authority on children’s literature.
Ms. Schwartz made her literary debut in 1982 with the publication of the picture book “Bea and Mr. Jones,” the story of a kindergarten-age girl who trades places with her father, reporting for work at his office while he, an advertising executive, goes to school in her stead.
The book landed a spot on LeVar Burton’s television show, “Reading Rainbow,” and marked the beginning of Ms. Schwartz’s long career in children’s literature.
Over the next four decades, she kept up a steady output of books — more than 50 in all — that showcased her narrative wit and artistic whimsy. The quality that most distinguished her work, however, was her sense of childhood, which remained undimmed despite the passage of time.
“I can’t think of anyone whom I think understood and portrayed the day-to-day routines of families with young children with more intelligence and joy,” Mary Cash, the editor in chief of Holiday House, one of Ms. Schwartz’s several publishers, said in a statement after her death. “Amy was an acute observer of all the tiny details that together make up a child’s life. Her wonderful books celebrated, laughed at, and offered so much insight into that existence.”
In the book “Busy Babies” (2019), she documented the many ways that babies fill their time — among them “visiting ducks” and “playing trucks,” “building blocks” and “removing socks.”
Her book “I Can’t Wait!” (2015), geared toward children who had advanced beyond baby- and toddlerhood to the more mature years of preschool, explored the interminable marking of time that children endure, often without knowing what they are waiting for.
In her “100 Things” series — including “100 Things That Make Me Happy” (2014), “100 Things I Love to Do With You” (2017) and “100 Things I Know How to Do” (2021) — Ms. Schwartz helped children scale that Mount Everest of early numeracy, 100, while also indulging their love of lists. (“100 Things That Make Me Happy” included “hula-hoops” and “double scoops,” “Grandpa’s tools” and “swimming pools.”)
Amid the hundreds of happy things in childhood, there are also plenty of hard ones, and Ms. Schwartz acknowledged children’s anxieties and embarrassments in books such as “Starring Miss Darlene” (2007), about an ungainly hippopotamus who, in one episode, is cast as “the Flood” in a theatrical staging of the story of Noah’s ark.
Rather than sprinkling some water on the stage, as her role dictates, she accidentally douses the front-row audience. A porcine theater critic takes a shine to Darlene, however, and lauds the show for its “audience participation.”
In her illustrations, Ms. Schwartz favored gouache, a form of watercolor, and pen and ink. The poet Eve Merriam, writing in the New York Times, offered a review in rhyme of the pictures in the book “Mother Goose’s Little Misfortunes” (1990), a collaboration between Ms. Schwartz and her husband:
Amy Schwartz’s pictures are buoyant, up in the airy,
goofy, guffaw-y, never too scary …
the watercolors are bright, there are white open spaces
to leave laughing room for the fuming faces,
the merry mishaps, the clown-y rages.
One capsule complaint: not enough pages.
Amy Margaret Schwartz was born in San Diego on April 2, 1954. Her father was a real estate investor and writer, and her mother taught chemistry at a community college.
The third of four daughters, Ms. Schwartz called upon her memories of her family for the volume “Annabelle Swift, Kindergartner” (1988), about a rising kindergartner and her worldly, wise older sister, who coaches her in what to expect.
Ms. Schwartz recalled that as a girl she was almost always reading. “I developed the ability to read while walking home from school,” she wrote in a biographical sketch, “as well as that of reading aloud to my grandmother and silently reading ahead, simultaneously.”
She also showed an early interest in drawing, keeping a sketchbook and taking art classes on the encouragement of her mother. Her first illustrations were birthday and holiday cards that she made for her family.
Ms. Schwartz studied drawing at what is now the California College of the Arts in San Francisco, where she graduated in 1976, according to an obituary printed in Publishers Weekly. She later took a course in children’s book illustration before moving to New York City, where she worked a clerical job while trying to make her way into publishing.
She began by offering her services as an illustrator and started drafting story manuscripts as well after editors advised her that she would have more luck if she marketed herself as an author and illustrator. She continued her studies in children’s literature at New York’s School of Visual Arts.
In addition to working with her husband, Ms. Schwartz collaborated over the years with her father, Henry Schwartz. Their books together included “How I Captured a Dinosaur” (1989), “Albert Goes to Hollywood” (1992) and “Make a Face: A Book With a Mirror” (1994). She worked with author Eve Bunting on the 1984 picture book “Jane Martin, Dog Detective.”
Among Ms. Schwartz’ more recent books were “13 Stories About Harris” (2020) and “13 Stories About Ayana” (2022), in which she chronicled the everyday adventures of two children in a diverse urban neighborhood. Harris, for example, uses sidewalk chalk to sketch a dragon whose tail is so long that it stretches up and down the block.
Besides her husband of 32 years, Ms. Schwartz’s survivors include their son, Jacob Marcus, of New York City; and three sisters.
Although she was roundly praised for her understanding of children, Ms. Schwartz displayed an equally intuitive understanding of parents. She wrote one of her best-known books, “A Teeny Tiny Baby” (1994), clad in her nightgown, in what she described as “one groggy stretch” in her son’s first weeks of life.
“I’m a teeny tiny baby,” read the book’s opening words, “and I know how to get anything I want.”
Elisabeth Bumiller, a Times journalist who is the author of two books about women and mothers, wrote in a review that her favorite illustration in the book depicted “a dark and silent Brooklyn street, lit only by the glow from the teeny tiny baby’s house.”
“In one window we see Mom quietly nursing, while in another stands Dad, staring into the distance and looking a little left out and perplexed,” Bumiller wrote. “New parents will instantly recognize that mix of confusion, exhaustion and intimacy that comes with the 2 a.m. feeding.”
In “What James Likes Best” (2003), Ms. Schwartz captured a universal experience of parenting: the execution of a maximally stimulating outing, followed by the discovery that your child was most entranced not by the wonders you had marshaled but rather something you had scarcely noticed.
The story, Ms. Schwartz said, was inspired by her own “endless quest to be the ideal mother,” and how she was over and again “humbled in [her] endeavors.”
She once took her young son to a sculpture garden only to find that the towering works of artist Isamu Noguchi held little interest for him compared with the hilarity of her accidentally turning on the windshield wipers in their car when it was not raining.
James, the character in her book, liked the windshield wipers best, too.