I found this book very enjoyable. John Postgate does an excellent job of describing the different types of environments that bacteria can occupy, from surviving in the deep-freeze arctic to boiling sulfur springs to mineral deposits buried deep within the earth. I was reminded of Stephen Jay Gould's "Full House", where he says that bacteria probably constitute the majority of the biomass of the earth. There's also an excellent chapter on flagella - and it was quite nice to see a good description at the molecular level of the flagella, along the lines of Michael Behe's description in "Darwin's Black Box".
One of the themes I found interesting in the book was that of evolution. He mentions examples of how bacteria might have evolved to digest nasty man-made organic chemicals in the environment, through natural selection of degradation pathways of similar molecules. Also presented is a "time-line", starting with the formation of the Earth and moon, about 4,500,000,000 years ago. Essentially bacteria appeared as soon as fossils could be formed - about 3,500,000,000 years ago, and for the next 2,500,000,000 years it was only bacteria, then a few small multi-cellular organisms, and it's only within the past 500,000,000 years or so that more complex organisms appeared (and really only the last 65,000,000 years saw the development of "modern" plants and animals). So essentially bacteria have "ruled the earth" for most of the history, and still occupy an amazing range of places and, as pointed out in Postgate's last chapter, the bacteria are still necessary for establishing new territory. So, for example, he says that in the future it might be possible to send bacteria to Mars or another planet to start preparing the surface, in terms of generating an atmosphere and also the beginnings of a biological ecosystem, for the eventual habitation of humans.
In summary, I would highly recommend this book!