If you are weak of heart, paranoid or just plain neurotic, Martin Rees' Our Final hour is not a book for you. In fact, this chilling and unsettling account of the threats humankind faces in the next few centuries reads more like a wild piece of fiction than nonfiction, and that is the scariest thing of all. The subtitle sums up what to expect when you agree to go on this haunting journey: A Scientist’s Warning: How Terror, Error and Environmental Disaster Threaten Humankind’s Future In This Century – On Earth and Beyond.

Rees, author of several books including the best seller Just Six Numbers, Gravity's Fatal Attraction and Our Cosmic Habitat, is a Royal Society Professor at Cambridge and England’s Astronomer Royal. He is also a great writer who has the ability to take hard science and theoretical conjecture and present them in simple layman’s terms. In Our Final Hour, he writes with expertise about the complex problems facing our planet and our species, including those we as humans are responsible for. Rees forecasts that the odds are no better than fifty-fifty that humanity will survive to the end of the 21st century, and then goes into great detail to describe the reasons why we are at risk -- everything from asteroids to terrorism to biological disasters to bizarre physics experiments that could one day backfire and end life as we know it within minutes. The stuff in these pages is terrifying yet amazing and intriguing, and it is hard to put the book down once you’ve committed to having your wits scared out of you.

Between startling scenarios involving nanotechnology gone out of control and lethal engineered viruses, crashing atoms together and creating bizarre “strangelets” that literally eat all mass, and biological errors that could kill millions, Rees runs us over the gamut of both natural and human potential for destruction and all-out Armegeddon, all the while maintaining the hope that we will realize how delicate our existence is and take the steps needed to ensure our survival…without stepping on and smothering science and freedom in the process. In fact, we learn that it is the human-induced pressures we put on our planet that threaten our survival the most, not natural disasters like earthquakes and tornadoes and hurricanes.

One learns some very shocking and fascinating things about what scientists are engaged in as they pursue knowledge, and where our species may be headed because of this rush to play God, but in the end, the book gives a feeling of hope for humanity, as I am sure Rees intended, by offering a positive outlook on what our future could be like if we stop trying to destroy ourselves, each other, and our planet and take responsibility for our roles as guardians of our environment. Yes, we are trying to crash atoms together and create computers that can think for us, and built in to those progresses are dangers we can only begin to imagine, but there are also benefits we can only begin to imagine. This is the balance Rees begs society to keep in mind as we continue to try and figure out the way things work and our place in the universe. Only when the risk of disaster is totally eliminated should we carry on with experiments and creations that break far beyond the boundaries of our current intelligence.

Ultimately, any fears I felt reading Our Final Hour (and there were many!) were alleviated somewhat by the realization that we, as humans, can stop the madness, if we truly want to. our Final Hour is one renowned scientist’s examination of the dire threats we face as humans on Earth, but also a call to arms, so to speak, to come together with the common goal of survival, prosperity and care for our planet even as we make leaps and bounds in science, technology and medicine.

The call has been sounded, and the end result will be based upon just how we choose to respond.