Theodor Seuss Geisel died in 1991, but his books continue to delight children across the globe. And come September, little readers will have the opportunity to delve into a never-before-seen world of Seussian wonder. As Minyvonne Burke of NBC News reports, Random House has announced that it is releasing a previously unpublished Seuss story about an art-loving horse.

The manuscript for Dr. Seuss’s Horse Museum, as the upcoming book is titled, was found in the author’s home in La Jolla, California, alongside the manuscript for the picture book What Pet Should I Get?, which was published for the first time in 2015. Dr. Seuss’s Horse Museum, according to Random House, features an “affable horse” who takes a group of students on a tour of an art museum. The book “marks a celebration of art and how we all see the world in different ways,” Random House says.

Seuss had not finished the manuscript’s artwork at the time of his death, so Random House recruited Australian illustrator and children’s author Andrew Joyner to complete the job. Beloved Dr. Seuss characters like Cat in the Hat, the Grinch and Horton the Elephant will make appearances in the story. Intriguingly, Dr. Seuss’s Horse Museum will also feature “full-color photographic reproductions” of “famous horse artwork” by the likes of Pablo Picasso, Jackson Pollock, the 19th-century French artist Rosa Bonheur, the American sculptor Deborah Butterfield and others.

The author was fascinated by modern art, and his own body of work expanded well beyond his children’s illustrations. At night, when he had finished working on his story of the moment, Seuss would create vibrant surrealist paintings, many of which featured cats, elephants and stags amid Dalí -esque landscapes. He also produced sculptures of fantastical creatures, made from papier-mâché and the bills, horns and antlers of animals that had died in the zoo where his father, Theodor Robert Geisel, worked. Seuss never displayed these works in public; he made them purely for personal enjoyment.

In a statement, Susan Brandt, president of Dr. Seuss Enterprises says Dr. Seuss’s Horse Museum may offer new insight into “how Ted thought about art, and how he viewed the world,” which she adds was grounded in “a creative eye, and a passionate belief in imagination.”