I read the Living Well With Hypothyroidism book, several years ago and loved it as well. Mary is sending me a copy of the new edition of that one, for a review that I'll be posting soon and a copy of one or two others I've yet to read. I haven't read her Hyperthyroidism/Graves' one yet and I may eventually get a copy of that one as well.
I've yet to see something I disagree with in Mary's books but I'm sure there are details here and there I'll have mild issue with. I'm sure I write things in articles that are disagreed upon, being far from perfect myself as well. Of course my reviews for anyone, will always point out the positive but I wouldn't be reluctant to discuss an issue I might see disagreement with in forum discussion.
I have also learned a lot from Elaine Moore over the years for example but have disagreed with a point or two she has made. I think people over-react at times when you express a disagreement on a forum for example and they instead think you cast dispersions on the person as a whole (my experience). I feel however that expressing disagreements on a subject, is healthy discussion, especially if it doesn't turn into attacks. It sometimes makes for interesting forum discussion and helps us gain better perspective on subjects!