Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Very interesting concept

This book was given to me by a friend I highly respect. When he gave me a summary of the book, I thought it was a little far fetched. However, as I began to read this first-hand account, my opinion started to change.Overall the book was an excellent read. Being that it was written in the mid 1850's, the language was a bit different from what we use today. Also, the author spends too much time, in my opinion, describing his journey into the earth. It would have been much better if he devoted more chapters to his experience while being inside for 2 years.