Can somebody help me generate ideas for a good fictional book/story?

I have always wanted to write a book and be published but don't really know how to go about it. The general plot/idea of my story is this: a girl and her mother move to america from england, after coming to the U.S. the mother becomes involved in a polygamist religion where the patriarch abuses and neglects her and lets his "main" wife run all over the others. Eventually she escapes. Any ideas?