Memory is inherently unreliable, constructed and encoded by perception and selection rather than by some objective recording process. So it is often the case that two people will remember a shared experience in completely different ways, changing their memories by collaboration and revision when they come together.
The notion of the unreliability of memory is a key theme in Julian Barnes' The Sense of an Ending, as well as the way in which we let our lives slip by us, burying hurt, pain and guilt into a comfortable complacency. Barnes' protagonist, Tony Webster, opens the novel by saying that "what you end up remembering isn't always the same as what you have witnessed." Though The Sense of an Ending is a complex book, it has a simple plot, with the complexity embedded in the unreliability of its first person narrator. Tony's self-delusion and discovery is as key to the unfolding as the plot which is revealed in simple recall.
Tony was part of a group of three pompously intellectual friends at secondary school, until a new boy, Adrian Finn, 'joined' the group, making it four. It was immediately clear that Adrian was the smartest in the group; clear thinking and serious. Together the boys ponder history, girls, and the limitations of their teachers, until one day a boy at school commits suicide. The boy, Robson, isn't well known, or flashy, but his death makes a significant impression on the boys. They move on to University, staying vaguely in touch until Tony finds a girlfriend named Veronica. Veronica is sharp-tongued and difficult, and ultimately leaves him for Adrian.
Meanwhile Tony moves on, gets married and has a child, and then divorces, staying good friends with his ex-wife. Which is, in some sense, the end of Tony's story. It's a potted life, with not much to talk about — certainly not the subject for a novel. But there's more. When Veronica's mother dies and leaves him a bequest and a diary, Tony suddenly needs to revisit his past to confront a growing unrest that his life might not have been as benign and peaceable as it appears.