This is a very good book on the mechanics of life. The author does an excellent job of explaining the the fundamentals of how we work at a chemical level. He writes in a very clear but sometimes lackluster style (given the obvious "affection" he has for the material). Plus he occassionally repeats the same point in consecutive sentences, which often made me feel like I was "fighting" this book.
One other item that the author probably had no control over: the print (in the paperback edition at least) was tiny. I'm 40 with pretty good vision, but still occassionally had to put this down for a few minutes to get my eyes to focus again.