I once read an Amazon list titled "Chesterton is the Besterton." Now I understand why.
The Napoleon of Notting Hill is set in an alternate 1984, one that isn't much different than 1904. Technology stopped progressing and most people stopped caring about government. Democracy has given way to despotism, because one idiot's opinion is as good as the opinion of all of them, to paraphrase the text. All of this changes when Auberon Quin is randomly selected as the King of England.
Python-esque humor abounds as Quin makes more and more ridiculous demands as a joke and commentary on how broken the system is. When he makes each burrough of London an independent nation, one man takes the joke seriously...
Chesterton's writing is good, both descriptive and full of dry wit. While much of the plot is whimsical, the battles are fairly well thought out and well written. The underlying theme of change being important is understated and never smacking us in the head.
In short, this is probably the best book I've read all year.