I read it first sometime in the late Sixties or early Seventies as an undergrad in engineering/physics/math. Carl Sagan created a wonderful book which has stayed with me over the course of almost 30 years now.
Tim NilesAn Absolutely Essential Read I first read this book in the early 1970s, and have read manysince then, and it pained me somewhat to find that the book is now out of print. I can honestly say this is still, without any doubtin my mind, the *best* starting place for the study of astronomy,cosmology, astrobiology/xenobiology (call it what you will) andall things extraterrestrial. The book gives you all the background information available at the time of its publication to understandproblems that are still profound to this day, in a step by stepmethod that is both an absorbing read and and a good bit of education in itself. Invaluable for both its conclusions and for the historical background it gives to current issues, well illustrated and beautifully far reaching, I most highly recommend this rare and wonderful book.