Harriet Brown is the author of "Brave Girl Eating" and an article on the Telegraph's website today gives you a summary of her experience. (Her book is about to be launched in the UK.) Well worth a read.
A book which we found really useful at the start, as UK-based parents of a teenage boy with anorexia, was Jenny Langley's "Boys Get Anorexia Too". At £21.84 from Amazon, it isn't cheap, but it was ten times more useful than some of the books we bought as part of our learning curve.
As a reminder, other useful books are: Janet Treasure's Skills-based Learning for Caring for a Loved One with an Eating Disorder: The New Maudsley Method and Lock & Le Grange's Help Your Teenager Beat an Eating Disorder.