Although not a perfect book, "The Age of Spiritual Machines" is destined (IMO) to become one of the more important books of the late 20th Century.
Kurzweil begins all the way back at the Big Bang, clearly unable to limit his scope to something more appropriate. He starts with an outdated summary of creation physics, then contrasts the slowing timeline of phase changes in the universe with the speeding up of the evolution of life -- as if the two are somehow related. He puts forth the curious idea that technology is "inevitable" wherever life evolves. Both these arguments exemplify the homocentric hubris that the universe was created for the emergence of mankind.
Nevermind. Skip the first chapter (as Kurzweil himself suggests in the prefatory note) and you'll quickly get into the good stuff. His chapters on the evolution of intelligence and the growth of computing power are well founded.
Where he really hits his stride however is in the second section, "Preparing the Present," where he puts forth cogent arguments for quantum computing based on DNA, mentality-enhancing neural implants, and "downloading your mind to your personal computer." He then goes on to discuss nanotechnology and life-extending technologies. This section alone is worth the price of the book.
After the past and the present, he gives quick snapshots of where he thinks we may be in 10, 20, 30, and 100 years. These too are well thought out and insightful. He is generally conservative, foreseeing no large "phase changes" which could radically affect current trends. It'll be interesting to check back to see how his predictions held up.
Other pluses: an excellent "further reading" list, extensive web links, and far-ranging footnotes.
Minuses: he takes Roger Penrose seriously, he fails to mention Racter in the discussion of computer authors, and he spends just a wee bit too much time tooting his own horn (Kurzweil Computer Products, Kurzweil Reading Machine, Kurzweil Data Entry Machine, Kurzweil Music Systems, Kurzweil Applied Intelligence, Kurzweil Education Systems, Ray Kurzweil Cybernetic Poet...) But to be fair, he HAS pioneered in all these areas, so perhaps he has earned his immodesty.
Overall, a fascinating, thought-provoking book which is not afraid to make concrete predictions. Given Kurzweil's track record, he may just prove to be 100% right.