The Memory Police by Yōko Ogawa
What if the government decided that what you could remember? What if they enforced people forgetting certain things? Memory is at the center of this dystopian story set on an island. At seemingly random intervals, people wake up and feel a loss of something. They feel something at the edge of their memory is gone. For example, one day they wake up, wander outside, and then struggle to remember what those winged creatures flying in the sky are called. If they have any books, or other references to that 'disappeared' thing, they have to quickly eradicate it before the Memory Police finds it. Not all citizens on the island are affected by the disappearances though; some people can go on remembering the things others have forgotten, but nobody knows why. The Memory Police is focused on trying to root out those people.