Long answer alert:
Frankenstein was written by Mary Shelly in 1860something (THe era is important)
So: the book is written in three narrators: Robert Walton- a seaman from London, Victor Frankenstein- a "Genevese" scientist and The Monster (Usually misnomered as frankenstein)
The book was written when England was very religious, and the idea of playing God (Creating a "human being") was out of the question.
Victor Frankenstein ( Im gonna call him VF for short) is a scientist that decides to make a creature out of "the loins of the dead". he succedes in this but then abandones his "wretch" when it wakes up.
You can use this bit in your exam.
The next bit is just going to be the general themes of the book:
Nature vs Nurture. is a person/beast bad from birth (nature, it is important to remember that the bodies that the Creation is made of are thoes of criminals) or Nurture (Victor abandons his "son")
That is baisically the biggest theme there is.