Call it literary archaeology: Dr. Seuss' widow, sifting through some of his papers, happened upon a manuscript she'd never seen before. Now, more than 50 years after it was written, What Pet Should I Get? is finally being published

In October 2013, Random House art director Cathy Goldsmith got a phone call. There was “a box full of something” at the home of the late Theodor Geisel—a.k.a. Dr. Seuss—in La Jolla, Calif., and his widow Audrey thought Goldsmith might like to see it.

“I went flying down the hall to my boss’ office and said, ‘They found something they want us to look at! We need to go to California!’ ” Goldsmith says. “We didn’t know what we were going to look at….[but] they don’t call like that very often.”

It turned out to be a nearly complete manuscript, written and illustrated, of a never-before-seen book. What Pet Should I Get?, out July 28, follows a brother and sister through the titular decision, from cats and dogs to fantastic Seussical creatures like the Yent (it sleeps under a tent).

Goldsmith, who worked with Ted, as she calls him, on his last five books, is a veritable Seuss scholar. She was able to date the What Pet artwork to between 1958 and 1962 by comparing it with his previous work. “First of all, the boy and the girl are absolutely, categorically the same two children we see in One Fish Two Fish,” she explains. “Those kids don’t appear anyplace else in his work. A couple of years later, his humans are starting to be looser and look a little different. In my mind, that says these two books were drawn very close together.” Another clue: The story is more narrative (as is earlier work, like The Cat in the Hat) than it is episodic (as is later work, like Dr. Seuss’s ABC).

Coloring the art was the next step. Goldsmith says Dr. Seuss was very particular about his hues. He labeled every drawing with specific tones, like a paint-by-number, to be filled in by the art department. In his mid-century work, the printing technology didn’t allow Seuss to use many mixed colors, such as brown, so Goldsmith scaled them back here, giving the book a retro but familiar feel. “He was a genius. He meant a tremendous amount, not only to the industry but to me personally,” she says. “So I feel an intense obligation to honor that and to get it right.”

A version of this story will appear in the August 7, 2015 issue of Entertainment Weekly. Pick it up on newsstands July 31 to see photos of the original manuscript next to the finished book, or subscribe online at