Mary Shelley's Frankenstein creates a very curious problem: who is the reader to blame? The necessary idea behind the answering of this question lies in the understanding of the question--who is to blame for what?
Victor is to blame for numerous things. First, he is to blame for desiring to possess forbidden knowledge. Without this desire, Victor never would have reanimated life. Second, Victor is to blame for the creature's abandonment. One could argue that if Victor would have embraced his "son" that none of "this" would have happened. Third, Victor is to blame for the deaths of William, Justine, Henry, Elizabeth, and his father. While not directly responsible, meaning the deaths were not by his hand, he is responsible for creating the being which was responsible for the deaths. Lastly, Victor is responsible for his own death. His great ambition, or tragic flaw, is directly responsible for his downfall and ultimate death.
The Creature's Blame
Directly, the creature is responsible for the deaths of William, Elizabeth, and Henry. Although he set up Justine as the murderer of William and she was found guilty, he did not physically take her life. Really, this is all the creature is directly responsible for. Indirectly, he is responsible for the deaths of Justine and Victor's father. Outside of these, the creature does nothing morally wrong.
In the end, one must decide what the true question is. Is Victor the reason why everything happened as it did, or did the creature's actions force Victor's hand?
In some way, both are to blame for different things.
For example, the monster is directly to blame for the deaths of both Elizabeth and Henry Clerval. He allows his anger at what Victor has done to him to overtake his ability to reason and leads him to murder as a form of revenge.
Ultimately, though, Victor is at fault for everything that transpires from the moment he reanimates the monster. He put the monster together without its permission. He gave it life and found that life so abhorrent that he refused to stay around to teach the monster any sort of higher reasoning (Right from wrong, etc.). As a result, the monster was forced to form its own version of right and wrong, which led to its murder of Henry and Elizabeth.