Instruct: Classify the given review as either positive or negative.
Query: WARNING: HARD BOOK!

I am a huge C.S. Lewis fan. I have read most of his works and I think they are great. This one is, on a scale from 1 to 10 in ease (1 being Dr. Suess and 10 being a Neurologists formal report) about a 9. Much more in depth than his other works I have read. A lot of backround knowledge is required. If you are a beginner I would suggest something easier and more fun to read such as "The Screwtape Letters" or "Out of the Silent Planet", for intermidiate I would suggest "The Great Divorce" or "The Four Loves". If you are advanced then go ahead and buy this one, I'll be puzzling over it for the next month.