Human race has warred itself to oblivion. The rescue comes from an unexpected source: as Earth turns uninhabitable, alien race Oankali rescue the few survivors and give the humanity a way to continue its existence.

Oankali, however, are traders, whose whole existence is based on trading in genes. This means that the humans must accept their ways: a forced symbiotic relationship, without which humans are unable to reproduce.

Each book of Butler's trilogy is a leap forward in time - the first happens after the main character, Lilith, gets woken up. In the next book, the focus is on her son, and the trilogy completes with her younger child, about a hundred years after the events of the first book.

More importantly, though, the point of view moves from human to more and more Oankali view. The picture the first book paints of the alien race becomes more and more complete, and at the same time, it gets harder and harder to like the new alien overlords.

It's a magnificently written book full of wonder, and while aliens are very much present, they are also used as an introspective mirror to take a look at humans. It describes a complex mesh of emotions, loyalty, biology and chemistry that drives people towards their various destinies, and really gives food for thought.