I wanted to like this book. It has everything I like in sci-fi: action, politics, and biological Armageddon. But I didn't like this book.

Half Life is set against a background where Earth is in crisis. For 200 years, new diseases have been ravaging the planet. After imploding, the population continues to decline to the point where the sick out-number the healthy.

Basic biological research is seen as the only hope for survival of the species. Multiple and on-going efforts are organized to try and untangle the whys and hows of life, in the desperate hope that some clue will lead to a solution to the pandemic. As part of that effort, a mission to Titan is organized to search for pre-life (why Titan? Who knows. It's not really explained). Of a crew of 50, only 2 are healthy, and over half are expected to develop one of the new forms of Alzheimer's before the end of the mission.

The story is fast-paced--almost too fast. Scenes shift quickly with little transition. I had to reread many sections because I lost track of who was doing what. Furthermore, the characters are interchangeable with no real personalities and only their specific illness and job distinguishing them from one another.

The presentation of the biological and chemical components of the story is difficult to slog through. There are two possible reasons for this: either the material is over my head or it is inadequately explained. Clement has an M.S. in Chemistry so the former is possible, even though I am a reasonably well-educated person. However, either reason results in an unsatisfactory reading experience.

The ending in particular is poorly explained--one crucial link in the biological and chemical concepts is glossed over, a rather critical oversight which left me with several unanswered questions. Furthermore, the book has several blatant typographic errors--which is striking since Clement specifically thanks the copyeditors in his acknowledgements.

Overall,the book has two things going for it: (1) the technology used to fly spaceship/jet hybrids on Titan is unique and scores very high on my "cool-stuff-o-meter"; and (2) it reads fast. Beyond those two elements, there's not much to recommend this book.