What is the top novel of all time? War and Peace? Moby Dick? Harry Potter and the Sorcerer’s Stone? Dream of the Red Chamber?
The answer is, of course, “it depends.” It depends on your definitions and measures. Sales? Number of copies published?
One way of measuring is to look at library collections. Libraries reflect popular interest. However, they also reflect scholarly and cultural interest over time. Libraries are where the world’s literature is stewarded and defined.