I enrolled on an evening course for homoeopathy. When the teacher offered to obtain Castro's book for class members, I declined as I already had a small library on the subject. I soon reversed this decision and it's the only book I consult now! It is the only book I have found that explains basics like the vital force, the minimum dose, constitution and susceptibility etc. There is a wonderful guide to taking a case as well as a dosage chart, potencies to use and sample cases that are actually useful! The bulk of the book is taken up with the Materia Medica which is easy to read and informative. After struggling on my own with fat erudite works, this shines a light in all the right places!