(Just my personal perspectives on the book - it'd be pretentious on my part to 'review' a stupendous work like Cosmos!)
For those with a taste for knowledge on the human endeavour of all hues, this book may leave them speechless! It's anyway a well-known work of epic proportions, but probably more well-known to people of a certain generation, who grew up watching Sagan, in his TV series of the same name, explaining it all back in the 80s.
The book is divided into 13 chapters (perhaps as a protest against the stigma and superstition attached to that number?, but more probably to fit in with a 13-week TV schedule). And it covers a mesmerizing array of human knowledge - from astronomy (of course!), to history (esp. of science), to anthropology, to mathematics, to logic, to physics and biology! Sagan takes us on a whirlwind tour of the cosmos itself, from the time when it was evolving out of the big bang to the birth of galaxies, stars and planets, from the primordial gases which arose first. Dropping down to the solar system, he traces its (short, in cosmological terms!) history, and then the evolution and stabilization of planets including earth.
While laying out the process of evolution of lfie on earth, Sagan keeps going back to the cosmos to prove that 'we're all made of stardust'. In between, he describes in fascinating detail how early scientists of millennia ago persisted in their pursuit of scientific knowledge, including the hardships (and sometimes bodily harm) they faced.
But beyond the rich scientific knowledge, most of all Sagan's book is an impassioned humanist plea. Woven throughout the book are his firm convictions on the unity of human race and the overarching need for tolerance and comity among nations, that the resources being wasted in a mindless nuclear arms race could be so profitably used in endeavours to know the cosmos better and thus benefit the human race as a whole.
As Sagan says towards the end, in the last chapter 'Who speaks for earth?': "We are a rare as well as an endangered species. Every one of us is, in the cosmic perspective, precious. If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another"!
This is a compulsory read for anyone with a passing interest in science and the human endeavour.