In some ways, quilters today have it so good with classes and tv and youtube! I started quilting just before the rotary revolution and so learned the how-to's to go along with my basic geometry knowledge, but you can bet I watched Sewing with Nancy to learn the latest stuff!
I've gotten rid of a lot of my quilt books, but one I kept and highly recommend as a reference book on things like different ways to make triangles or other ways to cut with rulers is Template-Free Quiltmaking by Trudie Hughes. Clear directions, helpful charts. I think she was the first or at least one of the first with "Around the Twist" and "Lover's Knot" which are in that book but there were other versions by other designers about that same time that are probably better known.
https://www.amazon.com/Template-Free.../dp/0943574374