I love to read, but often after spending an entire day at the easel have a hard time getting passed three pages, before my eyes are just too tired to continue. This is why free books on-line are of great value.
For example the Library of Congress has many very interesting books on a variety of subjects that are available for free download or to listen to on-line. I recently finished "A Manuel of Oil Painting" by listening to it while painting.
A great read for anyone who paints, the book is filled with wonderful information on how to produce better paintings.