The sketchbook is where an artist most often tries out new ideas. In a sense it's his or her laboratory for experimentation. In posting David's sketchbooks I have included many pages that he didn't sign, which was his usual stamp of approval. I did this because I think leafing through a sketchbook in its entirety, and seeing how ideas develop or change, can be rewarding and revealing.
A note on perusing the sketchbooks: The best way to go through them on this website is to pick a sketchbook, click on 'image gallery' button near the bottom, click on the first page image to bring it full screen, then scroll through the pages by simply clicking on your computers 'right arrow,' or back using your 'left arrow.' I hope you enjoy the ride. SL