The Quickening by Michelle Hoover

I loved the author's writing. So good, read it in one and a half days.
Two farm women living on neighboring farms in the early 1900's become friends of necessity. The story tells how their lives and families intertwined and the resulting tragedy and results.

Background on the book from the author (includes inspiration for the novel, reading guide for book groups):
http://www.michellehoover.net/real-life-story.html

Blog post by author about book groups who've read the boook:
http://www.michellehoover.net/blog/2011/01/why-i-love-reading-groups.html