From Atonement, by Ian McEwan. Some freakishly good writing, in my opinion.

"Was everyone else really as alive as she was?  For example, did her sister really matter to herself, was valuable to herself the way Briony was?  Was being Cecilia just as vivid an affair as being Briony?  Did her sister also have a real self concealed behind a breaking wave, and did she spend time thinking about it... Did everybody, including her father, Betty, Hardman?  If the answer was yes, then the social world, was unbearably complicated, with two billion voices, and everyone's thoughts striving in equal importance and everyone else's claim on life as intense, and everyone thinking they were unique, when no one was.  One could drown in irrelevance.  But if the answer was no, then Briony was surrounded by machines, intelligent and pleasant enough on the outside, but lacking the bright and private inside feeling she had.  This was sinister and lonely, as well as unlikely.  For, though it offended her sense of order, she knew it was overwhelmingly probable that everyone else had thoughts like hers.  She knew this, but only in a rather arid way; she didn't really feel it."