I had quite a bit of experience with horses before I got my own, but I wanted to build a personal library of horse-related books. The first one I got is "Basic Horse Care" by Eleanor F. Prince and Gaydell M. Collier. The second book I got is "Horse Owner's Veterinary Handbook" by James M. Griffin, MD and Tom Gore, DVM. My next books were "Birth to Two Years Old" by Cherry Hill; "The Complete Foaling Manual" by Theresa Jones; "Lungeing and Long-Reining" by Jennie Loriston-Clarke; "Mouth and Bits" by Toni Webber. I have several more, but those I've mentioned I have used for referrence most often.
I do believe that getting a foundation in personal research on the subject of horses then putting into practice what is garned from that self-education may not be a total lead to success. That is when another experienced horseperson or trainer is needed.