Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A GOOD SCI-FI READ

I thought book was a good blend of classic sci-fi with action and even humorous characters. Many good plot twists and turns written in Heinlein's unique style. Even today, I get shivers thinking about them. Weak ending in my view, however, makes this a 4 star to me rather than a 5 star. Anyone who likes Sci-Fi must read this.