I read it about 10 (ish?) years ago, but can't remember the title or author.
It's about people on a tube / subway train and each page is about a different person, who they are, their single / married staus, what they do and what they're thinking at the time and plan to do once they get off the train.
It was a mid-sized paperback and might've had the picture of the coloured tube map lines on the front of the cover.
From what I can recall, it's written by a man - possibly Canadian or American.
If you've ever got on a train a wondered what the person opposite does / is like this is the book for you!
Before this was a book it was an online interactive website that exploited the new web technology of hot links -- the website is still there so you can read the book online the way it was meant to be -- see http://www.ryman-novel.com/
There are 253 people on the train and each chapter describes a person in 253 words,