Overall a good book that all should read. It is a quest to bring constructive critical review (science) back into more widespread use.
Sagan spends too much time on debunking alien abductions and UFOs perhaps suggesting that this now 21-year old book is showing a little bit of its age. That said there are truisms throughout the book that have and will stand the test of time.
In the intervening 21 years, a lot of positive change has happened. The challenge for science that social pressures on kids not to be "nerds" has, for the most part, transitioned as nerds became geeks, and as such have gained notoriety and respect (as their prospects for earnings have grown).
Perhaps most haunting in our time was the foresight on what the lack of a scientific education might mean to our democracy. In reading the last two chapters (24. Science and Witchcraft & 25. Real Patriots Ask Questions) you cannot help but see happening before us now the very situations and consequences that he described as potentially happening.
Where I wish the book would have gone more in depth is the subject of Ch 17, The Marriage of Skepticism and Wonder. The focus of this chapter is a reminder to the critically inclined that we can be too quick to judge, to box potentials and alternatives out, and to set people off of exploration by consciously or unconsciously using very human social tools and desires to establish, maintain, and grow social status and provide ourselves with a degree of personal legitimacy and certainty. These are essentially the battlegrounds and weapons of the Great Culture War that we now find ourselves in and an area that the tools of science need not pick a side. There are no such things as "alternative facts" and this howler should be seen for what it is - an admission of lies. But our capacity to aim for our tribe to dominate also means that we use these tools sometimes not for the advancement of science but to squelch debate, to control the dialogue, and to gain advantage. The tools of science should not be seen to take sides in the culture war but should be seen as a means to negotiate the peace. We scientists have a responsibility to know this and to engage, in some cases, with a more open mind. Put another way, as the Zen master Suzuki Roshi put it, “In the beginner’s mind there are many possibilities, but in the expert’s there are few.” We need to use our scientific creed to keep open those seemingly unlikely avenues because foundational (paradigm) shifts do happen. But only when we choose to allow our beliefs to be challenged and to explore the possibilities with empathy, comradery and "the beginner's mind".