It's a simple title, right? The film's called Frankenstein, and it's about Frankenstein. Done.
But hold onto your brain for a second, Fritz. The film is called Frankenstein. But which Frankenstein is the title referring to?
Most directly, the title refers to good old Henry Frankenstein, the dude who makes the monster. The film is about the mad scientist who screws up…and about how he should stop screwing up and stealing brains, and should marry and settle down.
Frankenstein: the story of a romantic hero who needs to do more romancing and less grave robbing.
But Frankenstein could also refer to the monster. Yes, the monster's name is just "monster" (or "Mr. Monster" if you're feeling formal). But in popular culture that monster is often called "Frankenstein." In fact, in the play that Frankenstein is based on, characters sometimes referred to the monster as "Frankenstein."
Frankenstein: the story of a big monster who just wants to be loved (and maybe get a chance to destroy some things).
Finally, Frankenstein is Frankenstein. The film is based on Mary Shelley's famous book of the same name.
Frankenstein, therefore, doesn't just refer to the mad scientist dude or the monster dude; it refers to the whole story about those dudes, and how they make each other miserable. It lets you know that in this movie, you'll see mad scientists, monsters, mayhem, and scary things.
The title of Frankenstein says get ready to scream.