Drawing
Free to read here, from Project Gutenberg.
The Practice and Science of Drawing
The Crown of Wild Olive
Line and Form (1900)
The Elements of Drawing, in Three Letters to Beginners
A Treatise on Painting
The Theory and Practice of Perspective
Drawings in pen & pencil from Dürer's day to ours, with notes and appreciations
Drawing for Printers.
What to draw and how to draw it
A Handbook of Illustration
A theory of pure design
Der Weg zur Zeichenkunst