Mary Shelley's Frankenstein deals with themes that are universal and quite relevant even today to the modern reader.
The most salient themes involve the risks of tampering with nature's unique order, the dangers of ambition turning into obsession, and the necessity for human connection of any and every kind.
The risks of tampering with the unique order of nature is evidenced by the creation of the creature and Victor's insistence in testing the parameters of science. Like the old sayings go, "be careful what you wish for", and "do not tempt Karma". When someone attempts to make changes to anything that is already working (such as changes to the normalcy of life), then chaos is meant to follow.
The dangers of ambition are evidenced in Victor's obsession with creating life. It is an entirely different thing to be naturally curious than to directly perpetrate against an organized operating machine such as the human being. To make its tampering an obsession is a direct insubordination of ethics and to human dignity.
Finally, the human need for communication and connection is evidence throughout the entire story. We see that the monster, even when it opens its eyes, immediately seeks the touch of its creator, Victor. It was Victor's disgusted reaction what gives the monster its first indication of isolation and neglect. The monster then seeks a connection with the family in the cottage, and when it discovers how morbid he looks, he feels destitute by nature. He then asks his creator to make a female companion for him, for he sees that humans always make a connection. However, it is not to be. Eventually, the monster and its creator will continue to live a vicious emotional cycle of hatred and fear.
It is because these topics are so ardent to every society and so relevant to the human condition that the novel will continue to be considered a study in both human psyche, the human condition, and human emotion. All these are also top characteristics of Gothic literature.