The other side of things

The core theme of Frankenstein is, undeniably, Don't play God. One needs to mind their boundaries and respect them or else face horrible destruction, possibly by their own hand. Other themes can be drawn from the book, but they all bear a similar tone. One possibility that comes readily to mind is 'look before you leap'. If Victor had considered what he was doing before actually undertaking the project of creating the monster, he would have been spared years of torment and possibly gone on to live a normal, happy life.