Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Engaging, mysterious, facinating Cold War thriller

Four stars does not quite do this book justice. From the beginning the book unravels the story of a secret CIA operation during the height of the Cold War and a son's attempt to discern his father's role in it. The characters are well defined, each possesing traits characteristic of a hidden past, a parrallel to the book's theme. The action is fast and will engross the most passive reader, while historical accuracy combines with vivid imagery to present the action in a setting richly descibed by the author. Read the book while snowed in, you'll want to connect with the setting of Russia in winter and dedicate the time needed to finish this book.