I recently read and studied Catherine Gill's Powerful Watercolor Landscapes: Tools for Painting with Impact. This book stands tall above so many instructional art books for so many reasons. It's well written, the explanations are thorough and the examples of Cathe's work showcasing the principles are gorgeous.
I'm actually not much of a landscape painter (although this book has me rethinking that) but the lessons she explains so beautifully apply to all visual arts. She covers principles of simplification, good design, color, and creating with joy.
It's a real thinking artist's book and I loved it.
While reading her book, I kept a sketchbook of notes and exercises I did following along with the book. You can see my sketchbook by clicking here.
Thank you Cathe!