Norton Juster is an odd case. Very few people would recognize his name. Quite a few more would recognize the title of his most famous work -- The Phantom Tollbooth. I don't think it's a stretch to call that book a classic of children's literature; since its publication in 1961, several generations of children (and their parents) have been delighted by the adventures of Milo and Tock in the Kingdom of Wisdom.
Far less widely known but even more beloved is Juster's second great work. This is the illustrated story The Dot and the Line: A Romance in Lower Mathematics, first published in 1963. There's nothing else quite like it; something like 70 octavo pages, mostly paired as brief text with a facing illustration, telling the story of the hapless line who fell in love with a dot, and how he won her. I've seen comparisons with Abbot's Flatland, but I think they're fatuous -- Juster is on a completely different literary level. From the dedication(*) to the moral(**), it's a perfect gem of a creation. I'll quote the opening few pages:
Once upon a time, there was a sensible straight line, who was hopelessly in love
with a dot. "You're the beginning and the end, the hub, the core, and the quintessence," he told her tenderly, but the frivolous dot wasn't a bit interested,
for she only had eyes for a wild and unkempt squiggle who never seemed to have anything on his mind at all.
They were everywhere together, singing and dancing and frolicking and laughing and laughing and lord knows what else. "He is so gay and free, so uninhibited and full of joy," she informed the line coolly,
"and you are as stiff as a stick. Dull. Conventional and repressed. Tied and trammeled. Subdued, smothered, and stifled. Squashed, squelched, and quenched."
I can't possibly show the interaction between the text and the illustrations here, but Juster has great fun. It's a picture-book for adults, erudite and hilarious, and succeeds beautifully.
(As an aside, both of these works were adapted to film by legendary Warner Brothers animator Chuck Jones, of Bugs Bunny and Roadrunner fame.)
I have not read any of Juster's other, even more obscure fiction. There was a collection of stories, Alberic the Wise and Other Stories (1965), but everything else I can find seems to be either collections of cartoons with wordplay, or books for young children. I know nothing of these works. But I would argue that The Phantom Tollbooth and The Dot and the Line are sufficient.
(*) "To Euclid, no matter what they say"
(**) "To the vector belong the spoils"