I own quite a few books about the art of Frank Frazetta, but Rough Work just might be my favorite. It's such a treat to see pages from his sketchbooks, as well as roughs of his most famous illustrations. For some reason, I usually like an artist's sketches for paintings more than the paintings themselves. They are looser, and in Frazetta's case, brimming with vitality.
Frazetta also knew his roughs were often better, and he eventually started submitting roughs to his clients (paperback book publishers, and Creepy and Eerie) as finals.
From the forward, written by Arnie Fenner, There's this quote from illustator Roy Krenkel, who shared a studio with Frazetta:
At first we did roughs on everything and got them approved. Often the roughs were superior to the finished art. The roughs had more charm, more color, more everything. Then, finally, I gave up doing the roughs altogether. Frank would say, 'The hell with roughing this thing, that's doing it twice! You know I can do it. They'll take the final painting and like it – the hell with the rough!' And it worked.
Here are some sample pages (click for big):