Bestsellers endure for a reason—Murder on the Orient Express is an easy read. The language isn't difficult (Shakespeare, anyone?), the story is intriguing (even if it's slightly difficult keeping all the characters straight), and mysteries are good for stimulating the brain if the reader has any sleuth-like tendencies and wants to figure things out. It's also great for making inferences, because many of the statements don't make sense until later.

The book is a good example of the mystery genre, which can be exploited by focusing on story elements and plot development. You can take single scenes and examine how they fit into the story as a whole, why they're important, and how things would be different if they weren't included.