A very moving and intense story. Styron appears to break the rules (much like Elena Ferrante) in that he tells rather than shows. And parts of the story had a 'stream of consciousness' feel to it. But it all worked. It's not a light read, but quite dense. It's also not a novel that you can easily knock over in a day or so. This is because it provokes questions about the drive to live, the drive to death and how inhumanity and cruelty can derail the balance between these two drives, for both the subject of the inhumanity and cruelty, as well as the person imposing it.
Sophie appears to be aware of how her treatment at the hands of the Nazi's left her with deep inescapable wounds. However, this insight on Sophie's part does not ultimately help in their healing. She seems trapped in a 'victim mentality' that leads her to believe that love is possible with a tormentor. I felt that Sophie believed that her actions while in captivity had led her to believe that she didn't deserve to live (survivor guilt) and that Nathan's act in saving her meant that she was forever indebted and tied to him, in life and death.
I think the title is teasing us with the word 'choice'. While we are all masters of our own destiny to a large degree, circumstances can impose themselves on us in such a way as to make certain 'choices' inescapable, and so not choices at all. It is as if the word 'choice' in Sophie's case (and also at different times, other characters in the book) is a form of doublespeak leading to certain guilt and turmoil. The only choice that Sophie had in the passage to which the title directly refers to, was between two types of grief, loss and guilt that would carry either one of two different names. The 'choice' to experience these emotions was made for her and so was not a choice at all.
I don't know how Styron researched conditions in the concentration camps, and more importantly, its effect on those interred and what they did to survive, but it is a timely reminder how incivil and inhumane acts render all of us incivil and inhumane.