This book looks at the quality of line and different washes, comparing different media and styles to generate lines. Then looking at different media for the washes including watercolor, ink and acrylic.
It includes media that serve both purposes, such as watercolor pencils, non-waterproof inks and washes over pastel.
I didn’t feel the book had a lot to offer, but it is a quick and easy read and has nice art. I think there are better books to learn about line quality from.