The author has attempted to make a captivating but very technical subject accessible to the general reading public, with mixed success. I found it fascinating, but I have a math degree and was an A student in physics and astronomy; I suspect that others might find it too dense. The author makes a valiant attempt to make basic concepts understandable, including use of a great many metaphors and similes from everyday life, especially in the early chapters. Some of these could be helpful, I suppose, but I found them at times condescending (do we need to spin in an office chair with arms outstretched to understand you spin faster if you bring them in?), at times amusing, and occasionally confusing. The author often uses British colloquialisms for these, leaving a poor American like me to discern from context that a roundabout is not a traffic control device but some sort of merry-go-round. As for throwing a jelly at someone, I have no idea what that means; wouldn’t the jar crack his noggin?
Quickly, though, the author moves into the details of planet formation, fortunately without the equations. Rather, we must take her word, and that of countless other scientists, as to what is possible or impossible. For the 99.999% of us who can’t do the calculations ourselves, Clarke’s Third Law applies: the rules of planet formation are indistinguishable from magic. The problem with this is that what we/they thought was impossible is now being observed in distant star systems. Huge gas giants are orbiting very close to their stars. So are rocky superearth planets where they should not be able to form. There are planets whose density is between those of the rocky planets we know (Earth, Mars) and the gas giants we know (Jupiter, Saturn). So what are they made of? Water? Silicate rock? A rocky core surrounded by gas? What we “knew” about planets isn’t true anymore. The author explains all the theories that the experts have come up with, but she states right up front that we really don’t have good explanations for much of what the observational science is producing. The exciting part is that we are finding more and more exoplanets. New discoveries bring new knowledge.
If you are primarily interested in whether there is life out there or a planet capable of hosting us after we destroy the one we’re on, you’d be advised to skim liberally up to the last few chapters where these questions are addressed more directly. The short answer is that alien life is certainly possible, maybe probable, but it is unlikely to be in a form we could ever communicate with or even observe. A place where we could relocate would have to be closer to home and the only candidates seem to be moons within our own solar system, although none of them look all that promising. Still, it is amazing to consider all the factors that life as we know it require and how lucky we are to be in that Goldilocks zone. Once you do that, then consider those organisms like tube worms and anaerobic bacteria that do not require sunlight or oxygen. Life has a way of adapting to some very inhospitable environments.
The author and publisher have bravely aimed for what seems to me to be a very small slice of the reading public. The book is too simplified for researchers in the field and too technical for most other readers. She writes very well but there are a few errors. On p. 232 she states that the temperate zone in our solar system is conservatively estimated at 0.84au to 0.14au. That second number should be 1.14au. Otherwise we wouldn’t be alive. All in all I really enjoyed the book but I find it hard to recommend to most people. What I can say is that when you see the next headline that reads “Second Earth Found!” don’t believe it.