Discussions about anything are an integral part of understanding. Given that in literature everyone typically latches onto a different idea from the novel, discussions are important so that light may be brought to symbols, themes, or messages one might have missed during their own personal reading.
For example, if discussing a poem (given poems have different meanings for different people based upon personal interpretation) one reader states that the meaning of the poem is one about death another person may have thought the message was about life. The purpose of the discussion helps each reader to open their eyes not only to opposing or alternative meanings, but also allows them consider the text in a different way. This also helps others to, perhaps, "see" something they missed.
This being said, the importance of a Socratic circle is to fill in the chunks of information for everyone so as to create a complete understanding of the text as a whole. It is much like a math problem. While there may be one main message of a text, normally there are many underlying messages that add to the meaning as a whole. So where one person may have read a text and come up with a "formula" for the text, others may have the necessary pieces to complete the act of the "formulation." It takes many different point-of-view to create a whole.