Is it because the author is against the reader that you can't understand the book?
Not necessarily. There were many reasons for whether a book could be understood or not, such as reading difficulty, background knowledge, reading time, reading habits, and so on. Sometimes, the author might deliberately set up some puzzles or riddles to attract the interest of the readers or to explore the inner world of the characters. In this case, the reader may feel confused or difficult to understand. In addition, the reader's reading background and knowledge level would also affect their understanding of the book. If a person did not have the relevant background knowledge and reading experience, they might have difficulty understanding some complicated plots or character relationships. Therefore, not being able to understand the book did not necessarily mean that the author was against the reader. It depended on the specific situation.