This book is for people who like to think, are intrigued by the place of humans in the universe, are genuinely interested in the human condition, and/or find the history of humanity to be fascinating. There are also some interesting insights into Clarke's view on religion (which I pretty much agree with). For instance, on p. 23 he states, "Science can destroy religion by ignoring it as well as by disproving its tenets. No one ever demonstrated, so far as I am aware, the nonexistence of Zeus or Thor, but they have few followers now."
I have to agree with Clarke's intro disclaimer though that "the opinions expressed in this book are not those of the author". I doubt that Clarke really believes in the paranormal mumbo-jumbo that he uses to enhance the story. Some aspects of the plot reminded me of the famous Star Trek : The Next Generation episodes that dealt with the Borg.
I don't want to give away the ending or the plot so I'll limit my review to the above. This book inspired a Pink Floyd song by the same name and probably the third verse to Neil Young's famous "After the Goldrush".