Marghe is an anthropologist eager to arrive at the quarantined planet Jeep to study the inhabitants who have been cut off from Earth for several generations and mysteriously consist of only women.

A few years prior, "the Company" sent a team to colonize the planet but visitors were infected by a local virus that killed all men and 78% of women.

Marghe is received by the Commanding Officer of the remaining quarantined Company colony and sent out to study the natives and discern the mystery of their survival for generations without men.

I saw some similarities between Ammonite and The Left Hand of Darkness by Ursula le Guin. Both feature an outsider arriving on a planet inhabited by a lost human offshoot with variant gender distribution. The visitor in both have agendas that are abandoned as they become more sympathetic to the cultures they are studying.

This novel definitely challenges the notions of gender roles. She successfully imagines a world inhabited soley by women and avoids dividing them all into the roles traditionally assigned to men and and women.

Griffith is brilliant at character development. Her characters have psychological depth. The reader understands them and their motives, so when the characters are transformed, you know how much it means to them.