When the twins came back, it was a certain bet that Lola would still have to be found. Bound by an iron principle of self-love, she would stay out longer in the darkness, wrapping herself in some fabricated misfortune, so that the general relief when she appeared would be all the more intense, and all the attention would be hers. (1.12.5)
This is Emily Tallis thinking mean thoughts about her niece Lola, because she reminds her of her sister, Hermione. Emily imagines that Lola will fabricate misfortune to hog all the attention. The truth, though, is that Lola really does come to misfortune. The made-up version of reality isn't Lola's, but Emily's.
In Leon's life, or rather, in his account of his life, no one was mean-spirited, no one schemed or lied or betrayed. Everyone was celebrated at least in some degree, as though it was a cause for wonder that anyone existed at all. He remembered all his friends' best lines. The effect of one of Leon's anecdotes was to make his listener warm to humankind and its failings. (1.9.66)
Leon has one of the nicest versions of reality around. But… it's because he sees the best in everyone that he's friends with Paul Marshall and brings him to stay with his family. Even thinking the best of everyone has its downside, as it turns out.
Now there was nothing left of the dumb show by the fountain beyond what survived in memory, in three separate and overlapping memories. The truth had become as ghostly as invention. (1.3.16)
Briony is remembering the scene at the fountain, and also imagining Robbie and Cecilia remembering the scene at the fountain. She realizes that everybody has their own story going on in their own head, which means that everybody has their own version of reality. There's no one truth, so fact is just as much of a ghost as fiction. Briony finds this liberating and exciting. Having fiction treated as fact doesn't go so well for Robbie, though.
"It wasn't only wickedness and scheming that made people unhappy, it was confusion and misunderstanding; above all, it was the failure to grasp the simple truth that other people are as real as you. And only in a story could you enter these different minds and show how they had an equal value." (1.3.24)
This quote connects a number of themes—versions of reality, compassion, and writing. Writing is the way you acknowledge others's versions of reality and, in doing so, treat them with compassion. Briony's false accusation of Robbie seems to negate this insight—but the novel itself, Atonement, seems to be trying to fulfill it.
That the word had been written by a man confessing to an image in his mind, confiding a lonely preoccupation, disgusted her profoundly. (1.10.107)
The word Briony is referring to is the X-rated one that Robbie accidentally wrote to Cecilia. Briony sometimes thinks it's thrilling that other people have their own ideas and stories, but she also finds it off-putting. She seems as disgusted by the fact that Robbie's got images in his mind as by what those images are. The fact that he thinks freaks her out.
She was one of those children possessed by a desire to have the world just so. (1.1.4)
Briony wants to have the world just so… and the version of reality she gives us in the novel is just so in many ways. The book is very carefully structured in its own right, and we eventually learn that she's cleaned up the ending too. Even if she hadn't though, fiction is almost always neater than fact.
So many decent people could not be wrong, and doubts like hers, she's been told, are to be expected. Briony did not wish to cancel the whole arrangement. She did not think she had the courage, after all her initial certainty and two or three days of patient, kindly interviewing, to withdraw her evidence. However, she would have preferred to qualify, or complicate, her use of the word "saw." Less like seeing, more like knowing. Then she could have left it to her interrogators to decide whether they would proceed together in the name of this kind of vision. (1.13.51)
Briony gets tangled up in what happened outside her head and what happened inside it. Which is sort of understandable, since she's thirteen and in a traumatic and scary situation. The problem is that the adults involved also get confused as to what is happening in their heads and what might have happened outside their heads. The version of reality that traps Robbie isn't just—or even mostly—Briony's. That's why Cecilia is so mad at her parents.
Yes, and by the way, she also said that she's had a piece of writing turned down by Cyril Connelly at Horizon. So at least someone can see through her wretched fantasies. (2.100)
This is Cecilia writing to Robbie. She's arguing that Briony's writing is stupid and fantastic and unreal because it comes from the same place as her accusation of Robbie. Would Cecilia have liked Atonement if she'd read it? From this quote, it seems like probably not.
Periodically, something slipped. Some everyday principle of continuity, the humdrum element that told him where he was in his own story, faded from his use, abandoning him to a waking dream in which there were thoughts, but no sense of who was having them. No responsibility, no memory of the hours before, no idea of what he was about, where he was going, what his plan was. And no curiosity about these matters. (2.258)
Robbie is delirious here, and reality is drifting away from him. In other words, he's losing touch with his story, or his version of reality. This is what's going to happen to Briony, too, we learn at the end. Vascular dementia is going to erase her memories, and leave her adrift.
For three years she must have nurtured a feeling for him, kept it hidden, nourished it with fantasy or embellished it in her stories. She was the sort of girl who lived in her thoughts. The drama by the river might have been enough to sustain her all that time. (2.216)
Here Robbie remembers a crush Briony had on him, and wonders if that's the reason that she accused him. Briony herself suggests it was not (3.412). If Briony's telling the truth (emphasis on if), then Robbie's falsely accusing her as she falsely accused him. Except… Briony is writing this, remember. How does she know what Robbie thought of her? She may just be making it up—which means she's falsely accusing him of falsely accusing her…
[…] Briony already sensed that the parallel life, which she could imagine so easily from her visits to Cambridge as a child to see Leon and Cecilia, would soon begin to diverge from her own. This was her student life now, these four years, this enveloping regime, and she had no will, no freedom to leave. (3.16)
Briony's imagining two different versions of her life. In one (which she actually pursued) she became a nurse; in the other she went to Cambridge. Note that, though she says one life disappears, it isn't exactly gone. She's writing about it—it's still in the book. Is the life she didn't lead really less "real" than the life she did leave? Both are just stories in a novel, right? Which is the case for Robbie and Cecilia too. They only live in fiction—but they only died in fiction too.
I worked in three hospitals […] and I merged them in my description to concentrate all my experiences into one place. A convenient distortion, and the least of my offenses against veracity. (4.7)
Briony is saying she's told worse lies. She may be referring to the fact that in her novel she says that Robbie and Cecilia didn't die, but she also might be referring to the way she accused Robbie in the first place.