Shades of Grey is an unexpectedly devastating book. Funny as hell, yes, but with a creeping sense of horrors lurking just beneath the surface, and when they strike, well, they were even more awful than I'd been anticipating.
In the world Fforde creates, your place is society is determined by what colour you can see, and how much of it. The Greys are the working-class/serfs, and from there, social strata go up through the ROY G. BIV colour rainbow. Heavily hierarchical, your position is fixed at the time you take the Ishihara, the colour perception exam.
And the rest of society is heavily (and hilariously) regulated as well. No new spoons may be made, leading to a spoon black market. All towns must be on constant alert against the threat of ball lightning and swans. Ostriches do not exist. If you see one, it's Apocryphal, so obviously you don't see it.
In this world, Eddie Russett and his father are dispatched to East Carmine, his father to replace the local swatchman (read: doctor), and Eddie, to do a chair census, as punishment for a minor prank. Once there, Eddie is attracted by the nose of a cute grey servant, who threatens to detach parts of his anatomy if he so much as mentions her nose. Or does anything else.
While Fforde is setting up his surreal world, small daubs of what it would take to make this society run keep cropping up. As someone says near the end, when you set up a society to be long-term, rather than fair, any deviation from Munsell's Rules can get you sent to Reboot.
This is a hilarious dystopia, which is also horrifying. Just trust me, it can be both.