It started with alcohol.

In the spring of 1925, Theodor "Ted" Geisel was a senior at Dartmouth College. He spent his time in a fraternity and at the campus humor magazine, the Jack-O-Lantern. Ted submitted dozens of cartoons to the publication and eventually became its editor.

That's when he and his friends were caught sharing a pint of gin - in the middle of prohibition. They were in Ted's room. As punishment, he was kicked off the magazine.

But curiously, many drawings in his style still appeared in the next edition. They were signed with pseudonyms that an eagle-eyed reader might recognise as oblique historical references - L. Burbank, Thos Mott Osborne, D.G. Rossetti, L. Pasteur - but also, "Seuss".

The "Dr" part came later, followed by 44 children's books. This week, there will be a 45th: What Pet Should I Get? - a never-before-seen manuscript that Dr Seuss wrote and illustrated. Although he created the story sometime in the late 1950s or '60s, it wasn't discovered among his possessions until 2013.

Other manuscripts he wrote have published since his death in 1991, but none were illustrated by the author himself.

"This is the first found manuscript since his death that rings true," said Seuss biographer Judith Morgan. "I think it would please him."

Morgan is one of the few living people who truly knew the literary giant whose name every American recognises. She and her husband Neil, both journalists, were neighbours and friends with the man they knew as Ted since the '60s. After Geisel wrote his last book, Oh the Places You'll Go!, he finally agreed to let the Morgans write his biography, Dr Seuss and Mr Geisel. In the hours they spent interviewing him, they came to realise that his penchant for privacy came from a deep-rooted perfectionism.

Geisel used to spend hours standing in his office with his hands in his back pockets, pacing in front of his work, trying to think of ways to make it better. He would come up with multiple endings for his sentences, choose one, then change his mind. Once during their interviews, Morgan brought up that the original manuscript of The Cat in the Hat introduced his most famous character as "a cat" instead of "the cat".

"He threw his head back and looked puzzled and said, 'Is that better? I don't know! Is it better'?" she recalled.

The Cat in the Hat was the book that launched him into children's literature for good, Philip Nel, author of Dr Seuss: American Icon, said. Previously, Geisel worked in advertising to support his writing habit. He was the one to come up with the world's best-known bug spray slogan: "Quick, Henry, the Flit!"

"It was a national catch phrase, like 'Where's the beef?' or 'Just do it' or 'Got milk?' Everyone knew it," Nel said.

The success and loveability of Cat in the Hat or The Grinch overshadow much of Seuss' other lesser-known work, like his two books for adults, a live-action musical film and an Academy Award-winning documentary. During World War II, he drew more than 400 political cartoons for the leftist magazine PM. They look like black and white versions of his books, but with far darker messages. He drew a giant Yeti-like creature - labelled "Russia's Winter" - crushing a puny Hitler under its weight. Trees that look like the ones in Hop On Pop are gnawed down by a Nazi woodpecker as another bird in an Uncle Sam hat waits atop a tree nearby.

"After World War II, we see him bring those politics into his books," Nel said. "Yertle the Turtle is Hitler. The Sneeches is about opposition to antisemitism. Horton Hears a Who is about how everyone must speak up. That's a common theme in all of his activist books. Even the smallest, most insignificant person - children - have a role to play."

Dr Seuss and his first wife sometimes signed their Christmas cards, "With love from Ted, Helen and Chrysanthemum Pearl." There was no Chrysanthemum - they had no kids at all; it's believed that the couple was unable to conceive.

Still, "he had a total conviction that kids were great", Morgan said. "He believed in letting the imagination flow, and he thought it wasn't being encouraged enough by parents and teachers."

What Pet Should I Get? is a book that prods those childhood imaginations. When a brother and sister - familiar as the siblings from One Fish, Two Fish, Red Fish, Blue Fish - visit a pet store, they find a myriad of the made-up creatures that made Seuss so iconic.

The illustrations were found by Seuss's second wife and her secretary. They had been sitting in a box set aside after his death. And although they made a complete book, they were clearly unfinished: He hadn't yet coloured the pages or chosen the words from the multiple sentences he had laid out as options.

Random House's Cathy Goldsmith was tasked with making the book whole. This might have been controversial - a la Harper Lee's Go Set a Watchman had Goldsmith not worked so closely with Seuss for 11 years. According to the New York Times, she coloured Oh The Places You'll Go! under his direction when he was too ill to draw himself.

"He loved her and she knew him better than anyone," Morgan said. "Decisions had to be made in transitions, or which rhyme to use ... She had the best chance for getting it right of anyone living."

Because What Pet Should I Get? was written half a century ago, it's far from Seuss' final words. But when Morgan and her husband were conducting their last interview with the author, they asked him what those would be. Did he have anything else to say to the children of the United States?

Dr Seuss asked the journalists to let him think about it.

The next day, he handed them a yellow piece of paper on which he wrote:

"The best slogan I can think of to leave with the kids of the USA. would be: We can ... and we've got to ... do better than this."

Then he changed his mind, and crossed out "kids of the".

"The best slogan I can think of to leave with the USA would be: We can ... and we've got to ... do better than this."

THE WASHINGTON POST