I got this one recently, and in parts it's an excellent book. I would advise taking at least some of it with a grain of salt, though, as she does rather go on about the fictional Celtic Great Goddess and the equally fictional Tree Calendar a bit. She seems to take all sources as equally valid, citing authors like Robert Graves, Mary Daly, and Kaledon Naddair along side authorities like F. Marian MacNeill and Anne Ross and more technical documents like pollen studies.
This said, she seems to be an excellent source for Gaelic names of plants, medicinal traditions in the Highlands and Islands, and material regarding fiber arts and dyeing. She falls down a bit where she goes with Gravesian and NeoPagan sources for spiritual information. I feel that this is definitely worth the money, but one should take certain of her assertions with some caution.