253 by Geoff Ryman.
I was dubious when I started this due to the non-narrative, rule-bound writing, and sheer number of characters. There are 253 words about each of the 252 passengers on a London tube train, plus the driver. Each person is described according to a strict formula; their appearance, a short biography, and their thoughts at a certain point in the journey. You know from the outset that the train is going to crash. It was an internet book originally, so I'm not sure how much reading it in print might change the experience, but it works much better than I anticipated, and sucked me in quite easily.
There are some really clever and quite poignant plays on how the passengers (mis)read each other's appearance and behaviour once it becomes clearer which passengers are watching which other ones (now I wonder why that might appeal to me! ). I found the original internet version too (here), so I might have a look at that once I've finished the book. Not the most world-changing book in the world, for sure; but it's a nice little jaunt into something a bit unusual, and I think short enough that the formulaic structure won't get too get tiresome.
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