How does the creature learn to read? What might Shelly be trying to say about the creature?

The creature is basically self-taught. He learns to speak, and then to read, by observing and listening to the cottagers. He found a portmanteau that had several books in it, and he read them. He then read the letters that were in the pocket of the coat he had taken from Victor Frankenstein. I think the author is trying to get the reader to look beyond the creature's physical presence to see his intelligence and determination.