Instruct: Classify Amazon reviews into positive or negative sentiment
Query: great book!

This is a great book by a great scientist. Carl Sagan was also a first-rate explainer of scientific concepts and facts to laymen, as the late Isaac Azimov was. This book is endlessly informative as well as entertaining as it covers a wide array of subjects about humanity's interest in outer space and other related topics. It should be on everyone's book shelf.