Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: thought provoking

What is love? What is true sacrifice for a greater good? What is our relationship to things greater than ourselves? Big questions, and this novel makes you think about them, feel them, in a profound way. An alien race forces man to unite, and question our place in the universe, and in the end forces us to question the meaning of love for our children, and the meaning of ultimate sacrifice. Man becomes a Christ figure to higher intelligence. I wasn't surprised to see C.S. Lewis praise this book, although it is not really religious, or meant to be any sort of Christian allegory. I've read 20 sci-fi books, and love PKD, but this one has true staying power. But it was also easy to read, and engrossing -- and in the end profound. A great sci-fi book for people who want to sample the genre.