The flaw with this book is that it's not going to be read by the people who ought to read it. I thought it was well written, argued sensibly, and basically agree with almost everything that Carl Sagan writes. But in a certain sense, many of the ideas and concepts were not new.
Bits that did stand out include:
An excellent description of the broad open mindedness and skepticism that are both essential ingredients of good science. You have to always be willing to consider new hypothesis, and to look at data in a new light. But at the same time, you have to be ruthlessly skeptical in order to weed out ideas that don't work. This isn't easy; scientists are human too and suffer from the same defects we all do.
This is one of the reasons that the organized religions do not inspire me with confidence. Which leaders of the major faiths acknowledge that their beliefs might be incomplete or erroneous and establish institutes to uncover possible doctrinal deficiencies?The theories scientists hold on any given day are less important than the methods behind science. Theories can change depending on what's known at a given point in time from observations and experiments, but the relentless method of seeking the truth is what sets science apart: there is a method for sifting through the facts and arriving at what is the most promising theory, and those theories must change when new data arrives that contradicts them.
In any event, lots of sensible ideas about the importance of science to society, and a passionate defense of science as an institution of human progress.
The problem though, is that the book likely won't convince anyone. If you're convinced that evolution is the work of the devil, logic and reason are not going to phase you. If you're on board with the idea of science, you'll nod in appreciation, but not learn much that's new. It'd make a fantastic book to give, say, high school students to read and discuss, but it's probably way too "controversial" for that.