Instruct: Classify an Amazon review into positive or negative sentiment.
Query: CCNA Study Guide Rip Off!

There seems to be a lot of sales hype in the form of apparent 'customers' recommending this with testimonials, but I've found the materials are incomplete and loaded with errors; the testimonials are obviously bogus! Then comes the added insult of trying to communicate, but Mr. Lammle refuses to try to correct his materials, or even discuss this; no, he has 'banned' criticism! Beware!