The children's book, entitled "Dr. Seuss's Horse Museum," will be released on September 3 by Random House.

"Dr. Seuss's Horse Museum" is based on a never-before-published manuscript and sketches from the late children's author, whose real name was Theodor Seuss Geisel.

The long-lost manuscript was rediscovered in 2013 by the author's widow, Audrey Geisel, in the couple's former home in La Jolla, California.

It was housed in an overlooked box along with a nearly complete version of "What Pet Should I Get?", which was published in 2015.

"Dr. Seuss's Horse Museum" follows a horse who takes children on a tour through an imaginary museum, which only exhibits equine-based artworks.

Among them are Franz Marc's "Blue Horse I," Mané-Katz's "Bedouins on Horseback (Racing)," Edouart Manet's "At the Races," and Edvard Munch's "Horse Team."

As pointed out by Artsy, publisher Cathy Goldsmith was first surprised to find out that the manuscript centered on horses -- an unusual subject matter for Dr. Seuss.

"Ted didn't draw horses very often. He drew cats, he drew dogs, he drew cows. [But] when you think about it, it makes perfect sense for this project," she noted.

Goldsmith believes that Dr. Seuss began the manuscript in the mid-1950s, as he wrote and starred in a short-lived TV special called "Modern Art on Horseback."

"Dr. Seuss's Horse Museum" features illustrations by acclaimed Australian illustrator Andrew Joyner, who took inspiration from the late author's original sketches.

For the book, Joyner created a series of full-color photographic art reproductions of pieces by Picasso, Jackson Pollock, George Stubbs and other artists.

Fans of the Seussian universe will be delighted to notice cameo appearances by the Cat in the Hat, the Grinch, and Horton the Elephant.

"Dr. Seuss's Horse Museum" will be published on September 3, with pre-orders already available.