Don't be put off great texts by unpleasant childhood memories of ploughing through musty old classics. Modern translations of the classics are often very readable, and if you are interested in the topic, even 'dated' writing can have a certain charm. One of my favorites is Leon Battista Alberti's "On Painting", in a rather dog-eared 1966 edition translated by John R. Spencer, and its an absolute gem. It might be 'On Painting' but there are gems of insight that you'll value, whatever your medium. For example, Alberti's observations on light:
"....remember, never make any plane so white that it cannot be made whiter. If you should dress a figure in the whitest robes, it is best to stop much below the highest whiteness. The painter has nothing other than white with which to show the highest lustre of the most highly polished sword, and only black to show the deepest shadow of night. "
These observations are fundamental to the successful use of light and dark in a drawing, and should be given some thought by beginners. One of the common beginner drawing mistakes is to draw far too lightly, and not to exploit a full range of value.
Find free classic texts online:
Alberti - On Painting online version.
Pen Drawing by Charles Maginnis on Gutenberg
The Practice and Science of Drawing by Harold Speed