I've been following this plagiarism business a while now. Today it was announced that Cassie Edwards and her publisher have parted ways over the allegations. Obviously, they are of a different mind regarding fair use. It's brought up the question for us writers: What constitutes plagiarism? A court in England found Dan Brown not guilty in the case of The Davinci Code; and as far as I can tell, these two cases differ only in the fact that Cassie Edwards didn't include a bibliography giving credit for her nonfiction references.
I read everything written by the late Eugenia Price, and she went into exhausting detail in her afterwords about the sources of her material. Sometimes she included entire texts of actual letters in her novels. I certainly didn't think of Eugenia Price as a plagiarist, just a historical writer thorough in her research.
Cassie Edwards, whom I've never met and don't know, has written lots of books depicting the native American people in a sympathetic and realistic light. I suspect she sincerely thought she could use the research materials in her fiction. I hate that her writing is now tainted by this charge of plagiarism. I guess the lesson here is to cite all your sources. Then be sure your publisher includes your remarks in the finished product.