Ian Falconer, the author and artist whose Olivia series enchanted young readers for more than 20 years, has died at 63, the New Yorker reports.

Falconer, a Connecticut native, studied at New York University, the Parsons School of Design, and the Otis Art Institute. He was living in Los Angeles when he befriended the legendary painter David Hockney, with whom he collaborated on designs for stage opera sets.

He illustrated covers for the New Yorker before making his literary debut in 2000 with Olivia, recounting a day in the life of an adorable piglet. It was named a Caldecott Honor book and became a bestseller; in a starred review, a critic for Kirkus praised Falconer’s “flawless decisions in composition and page design.”

Seven more Olivia books followed, including Olivia Saves the Circus, Olivia Forms a Band, and, most recently, Olivia the Spy.

In an obituary sent to Kirkus, Falconer’s friend Jeffrey Whitty wrote, “He balanced bright, boyish curiosity and the wisdom of a grizzled sage. His compassion for emerging artists made him a natural mentor, sparking fast friendships that spanned decades.”

On Twitter, journalist Benjamin Ryan wrote, “I am deeply saddened to learn that the great Ian Falconer, illustrator [of] the beloved Olivia children’s books and myriad New Yorker covers, as well as a designer of ballet sets and costumes, has died at 63. He was my friend and neighbor and kindly signed many books for my nieces.”

And author Kristan Higgins tweeted, “Rest in peace and joy, Ian Falconer. Thanks for Olivia. We loved her (and you).”

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.