Instruct: Classify Amazon reviews into positive or negative sentiment
Query: why pay money for free information?

Ok he knows how to do caving, but he can't put it in words as a good author should be. Wait I was told he isn't an author at all, he is still a student for the last 30 years.If you want free caving advices why not reading into urban exploration, as they do caving all day long. And this is were Greg got his information from as well.So don't read from the middleman if you can get the information from it's source.