Spending a significant amount of time with someone is necessary to get to know their personalities and temperaments. Sometimes, people can also tell a person's quality and determine his or her personality by analyzing their behaviors. When it comes to the question of whether one can learn about another person from the books or movies that the person likes, I personally am in favor of this statement based on the following reasons.
First off, by judging from the books or movies or even TV programs that someone like we can tell a person's interests and hobbies, consequently we can learn more about them. For example, My roommate back in college was really into auto magazines, TV shows and even movies featuring fancy sports cars. At first, I didn't know him so well to know his hobbies and interests, however, I was sure at that time that he must have been a big fan of cars. Indeed, my judgment was right and he was a car freak, he likes all kinds of vehicles like sedan, SUV, recreational vehicles, etc. It is not an exaggeration to claim that he can tell not only the brand but also the version of a specific vehicle by just checking out the picture of the cockpit of the car. Ultimately, we can tell a person's hobbies by the movies and books they like.
Additionally, the genre of the books that someone reads says a lot about the person's character and temperament. Actually, it is natural for someone to shape their characters just because the characters in the novels or movies have a dramatic impact on the person's behavior and attitude, regardless of the types of the characters like fairy, alien or someone with superpower. For instance, girls who read a lot of romantic novels like Gone With the Wind might be very emotional and very committed to someone they love. For someone who read science fiction novels or watch movies featuring future events and exploration of outer space tend to be very creative and willing to take risks, to be more specific, they might be someone who friends can depend on when they got stuck in some sort of exploration.
For someone who likes to read classics of all times like the works by Jane Austen or Ernest Hemingway, they tend to cherish the simplicities and trivialities in lives.
In a nutshell, by judging from the genre of the book that someone reads, not only can we tell a lot about the person's interests and hobbies but also the person's character and temperament.