Reddit mentions of A Door Into Ocean (Elysium Cycle (1))

Ishmael was the first one that I thought of too. And Margaret Atwood is great (Oryx and Crake is my favorite).

Also - [A Door Into Ocean] (http://www.amazon.com/Door-Into-Ocean-Elysium-Cycle/dp/0312876521)

Since you got the obvious one out of the way, I'll add Diana Wynne Jones, most known for the original Howl's Moving castle book series. For the older, witchiest readers I'd highlight "A Sudden Wild Magic" a less child-friendly story about a coven of new age practicioners facing off an attack on their dimension.

For the sci-fi fan, A Door into Ocean written by science witch Joan Slonczewsky

and most stories by Vonda mcIntyre many of which can be found online (in googling this I just learned she passed this spring :( )

She writes about biology, aliens, sex, centaurs, alien sex, genetic manipulation and marvelous winged sapients. There is a peculiar wistful melancholy to her stories. A good starting point is the short story "Of Mist and Grass and Sand" that segues into the novel Dream Snake, a story about a wandering healer and her three snakes with various "medicinal" bites.

A Door Into Ocean by Joan Slonczewski. There's a tiny bit of space in it, as the ocean world is the moon of another planet. The author is a Quaker and a microbiologist and she creates a very compelling ocean world and a unique nonviolent society.