Two more themes that appear in the book are the idea of beauty, and the concept of playing God.
Beauty applies in several ways, but the easiest is no doubt the idea that society of the time, much like now, sees only beauty as being worthy, and those people that are ugly (or what society considers unattractive) have less value. Today, that's obvious, with so much media focus on how things look. In the Monster's time, though, it obviously still mattered. There's no doubt that the monster is intelligent and has within him the ability to be compassionate and a productive member of society. The repeated reaction to his appearance removes those traits from him.
Playing God is another theme; obviously, the results of human beings playing God can never be good, and therefore, we must leave it to the "real" creator to do just that. Keep in mind, that's what the book is saying, not necessarily how I feel about the subject. Another thing to consider is just how disgusting the whole process of building the monster is, and the end result is far less elegant than human beings are. In a time of beauty, the Monster's lack of it illustrates how we should never attempt to play God.