Stories like this give me the creeps! Basically it is about a man who decides to join his consciousness with a computer. You can think of the author's message as the themes of the story. The themes are similar to other science fiction. Our humanity is unique, there is a distinction between love and compassion, and just because you can do something does not mean you should. To me, these are the messages of this story. Science fiction is an exploration of humanity. Clarke wants us to put ourselves in the position of wondering what we would do, and what the future might hold. Here is another discussion of themes: http://www.enotes.com/2061-odyssey-qn/themes