I'm not entirely sure about the exact selection process, but it likely involved a panel of literary experts who considered various factors such as the novel's influence on literature, its artistic merit, and its cultural significance.
The selection probably took into account how a novel had contributed to the development of the novel as a literary form. For example, novels that introduced new narrative techniques or explored complex themes in unique ways were more likely to be included. Also, the popularity of a novel over time and its impact on different generations of readers were likely considered. Novels that had inspired other writers or had a significant role in different literary movements, like modernism or post - modernism, might have been given preference.
It could also be that the novels were chosen based on their ability to stand the test of time. Novels that remained relevant and continued to be read and studied years after their publication were more likely to be part of the list. Additionally, the diversity of voices in the list might have been a factor. There are novels from different cultures, time periods, and literary traditions, which shows that the selection aimed to represent a wide range of the best that literature has to offer.