Nebula and Hugo award winner in 1972 and 1973. Humanity finds an unlimited source of energy, but it will destroy the sun. The book is divided in three parts, each presenting a different viewpoint: a young scientist trying to convince of the danger, the aliens responsible for the energy source and a scientist on the moon with the help of a female intuitionist.

If you like Asimov’s style, you will like this book. If you don’t, the book has the same flaws as most of his writings. Character development is limited. Most of the book deals with side stories. The first part ridicules the ego and lust for fame of scientists. Asimov then describes a strange alien society where they live in groups of 3 (a Rational, an Emotional and a Parenting), how they make love and evolve to another form after they have 3 children. The last part is about the difficulties involved living on the moon. The “real” story occupies a tenth of the book and there isn’t much development, other than finding a solution.

I personally love Asimov’s imagination and I couldn’t stop reading once I started, always a sign of a great book. 4.5/5 stars.