Faith and the Placebo Effect by Lolette Kuby. The author's personal experience was with cancer, but her theories apply to every health condition.
With MS we get so scattered and fragmented keeping up with research, changing our individual tactics, etc. This author's ideas have helped me streamline some of the mental clutter and focus on the larger most important part of the picture.
Don't be put off by the title. Well researched, well written.