Review the main characters of the story with your students and make sure they have a good understanding of them. On a quiz, you can ask questions such as "Who is Erik?" and "Who is Christine?" Ask about the personalities and physical traits of the characters to evaluate your students' attention to details in the story. For example, ask the students to describe the main elements of Erik's deformity. You might also ask them to compare the characters in the original Leroux novel to those in the popular stage version by Andrew Lloyd Webber. For example, Webber's characters are more romanticized.
Review the general plot of the story with your students. Rather than going over the whole story when the students have completed the novel, you may wish to do it a chapter or a section at a time based on your student's assigned readings. Make sure they pay attention to key events in the book, such as Christine's kidnapping, the gala event or the falling of the chandelier. If you are studying other versions of the story along with Gaston Leroux's version, be sure to have your students compare and contrast the different versions.
Some of the main themes of "The Phantom of the Opera" are obsession and possession, horror, appearance and reality, pride and jealousy and the human psyche. You might discuss topics such as why Christine stays with Erik even when she is terrified of him, characters in the story who are motivated by jealousy or what role Erik's deformity has played in the way he lives his life. Have the students identify themes and give examples from the text to support their examples.
Setting plays an important role in any story, and thus it is critical for students to understand it. The majority of "The Phantom of the Opera" takes place at the Paris Opera house, and is split between the surface of the Opera House and Erik's dwelling beneath it. Discuss the contrast between the world Erik has created beneath the Opera House as compared to life on the surface. You might also discuss the time period in which the novel takes place and how that might effect the story.