One well-known series of his is "Mr. Pine," for preschoolers.

There are many read-alouds of his books on YouTube.

http://www.google.com/search?tbm=isch&hl=en&source=hp&biw=1024&bih=578&q=leonard+kessler&gbv=2&oq=leonard+kessler&aq=f&aqi=g-S4&aql=1&gs_sm=e&gs_upl=1276l3177l0l3513l15l13l0l5l5l0l176l1177l0.8l8l0
(book covers & photos)

https://www.washingtonpost.com/obituaries/2022/02/25/leonard-kessler-childrens-author-dead/

By Emily Langer.

Excerpts:

Leonard Kessler, an author and illustrator who created more than 200 books for children, including an enduring classic, “Mr. Pine’s Purple House,” whose simple words and pictures encouraged readers to show their singular splashes of color in an often conformist world, died Feb. 16 at his home in Sarasota, Fla. He was 101.

His son, Paul Kessler, confirmed the death and said he did not yet know the cause.

Mr. Kessler credited his long and prolific career in part to his grandmother, a painter who gifted him a box of crayons when he was 6, declaring that “with these … you can paint your own world.”

As a college student in Pittsburgh, Mr. Kessler befriended future pop artist Andy Warhol. He later found his own calling in children’s literature — that magical genre offering young readers an introduction to the written word, an explanation of life around them and a glimpse of the universe beyond it.

Mr. Kessler collaborated on dozens of books with his wife, Ethel Kessler, a social worker and kindergarten teacher. Aside from his artistic flair, he brought to his work the ability, so rare among adults, to genuinely relate to children, their curiosities and their concerns. Such was his desire to understand their world that he sometimes crouched down to experience life from their height...

....Tastes in children’s books change as quickly as the youngsters who read them, and “Mr. Pine’s Purple House” fell out of print by the 1970s.

Two decades later, a mother named Jill Morgan, who had loved the book as a girl, looked in vain for an affordable copy for her children. Used copies were available online, but with price tags reaching into the hundreds of dollars.

Through some sleuthing, Morgan located Mr. Kessler in Florida — he was nearly 80 at the time — and asked if he might agree to a reprinting.

“Certain angels come into our lives at the right moment. She gave me back my life again,” Mr. Kessler told the Tampa Bay Times in 2005..

With its reissue in 2000, “Mr. Pine’s Purple House” became the first book published by Morgan’s Purple House Press, which specializes in formerly out-of-print children’s books.

Among the original fans of “Mr. Pine’s Purple House” was Jeff Bezos, the future founder of the online retailer Amazon and owner of The Washington Post. According to an account published in the Atlantic, Bezos’s mother discovered the reissued version after its release in 2000 and alerted her son, who promoted the book in a weekly email to Amazon customers — sending it to the site’s bestseller list.

Bezos again championed the book in 2014 with the rollout of the Amazon Fire Phone, a failed foray into the smartphone market. In advance of the product’s release, technology journalists received a package from the company with a letter from Bezos that read: “Enclosed is my favorite childhood book — Mr. Pine’s Purple House. I think you’ll agree that the world is a better place when things are a little bit different.”...

....Mr. Kessler served in the Army during World War II and was stationed in Europe, where he served as an infantry scout. Because of his talent for art, he was charged with drawing maps and sketching enemy positions. Years later, he recalled his habit of embellishing his military sketches with drawings of animals and flowers.

“Kessler, I just want to know the positions!” he recalled a captain admonishing him. “I don’t need the decoration!”

After the war, Mr. Kessler studied painting and design at what is now Carnegie Mellon University in Pittsburgh, where he met Warhol and the future painter Philip Pearlstein. After their graduation in 1949, the trio moved to New York City.

“I came with my wife and worked at home as a freelance writer and illustrator of books for kids,” Mr. Kessler told the Sarasota publication Attitudes Magazine in 2006. “Phil wanted to be a graphic artist. I wanted to be a painter. And Andy didn’t know what he wanted to be. He had one white corduroy suit [and] the biggest portfolio of the most incredible drawings and paintings.”...

....Mr. Kessler’s children inspired many of his books, including “Here Comes the Strikeout,” first published in 1965 and reissued in 1992 by HarperCollins. As a Little Leaguer, his son was reduced to tears after striking out 22 times in a row, Mr. Kessler told an interviewer....

https://www.nytimes.com/2022/02/24/books/leonard-kessler-dead.html
By Penelope Green.

....When his young son Paul asked him, “Do baby bears sit in chairs?” Mr. Kessler replied, “I don’t know, but that’s a great title for a book.” (“Do Baby Bears Sit in Chairs?” was published in 1961.)...

....A few years later, in 1953, the Kesslers decided to sublet their apartment to Mr. Warhola (by then he had changed his surname to Warhol), who needed a bigger place: His mother, Julia, was coming to live with him, along with her 25 cats, all named Sam.

The Kesslers moved to New City, a town in Rockland County, N.Y. (and into a house they painted pale purple). Mr. Warhol, his mother and the cats all moved into the apartment. But Mr. Kessler kept one room there for his studio and commuted from the suburbs.

Mr. Warhol’s mother was a cheerleader for both artists: “Andy, work! Kessler, work!” was her daily greeting. As for the cats, which she described as “the good Sam … the bad Sam … the crooked eye Sam … the fat Sam” and so forth, they ended up in a book. Mr. Warhol self-published “25 Cats Name Sam and One Blue Pussy” — his mother did the calligraphy — and gave copies to friends like Mr. Kessler.

In 2006, Mr. Kessler sold his copy, along with a self-portrait that Mr. Warhol had given him, at Sotheby’s. The proceeds allowed him to stay in his own home, with care, until his death....

https://www.publishersweekly.com/pw/by-topic/childrens/childrens-industry-news/article/88657-obituary-leonard-kessler.html

https://groups.google.com/g/rec.arts.books.childrens/c/c5t4CKuP49o/m/yCHF-1j9AQAJ
(birthday post from 2020, with booklist, reviews, and interview)