Instruct: Classify Amazon reviews into positive or negative sentiment
Query: SF classic

Every so often, I like to come back to this book and give it a quick read. I first read it when I was about 10-11 years old (back in the late 50's - I'm dating myself). Yes, there are a few things that today seem rather dated, but even now I am amazed how plausible Heinlein makes everything seem (especially in 1953)! The notion of accelerating to light speed and finding a pre-calculated "short-cut" in space (black hole?) is still intriguing. This is a solid entry in the Heinlein canon of great stories.