I have a bunch of favorite books that I enjoy rereading over and over again. Not a big fan of biographies, but theory and how-to books are my jam. I own basically every book my Cherry Hill. Many of her books are aimed at either complete beginners, or are best used as a reference for some type of project (building a barn, buying a trailer, etc.).
I really like Sean Patrick’s Countdown to Broke. The writing is very clear and accessible. Patrick’s breakdown of his training method is a good starting point regardless of discipline.
My second favorite book to reread is about the Masterson Method of equine massage. It is a fun, low-stakes topic to learn about and comes with tons of pictures.