The nature and art of workmanship

is an excellent book by David Pye (isbn 1-871569-76-1). As usual I'm going to quote from a few pages:
Design is what, for practical purposes, can be conveyed in words and by a drawing: workmanship is what, for practical purposes, can not.
The essential idea is that the quality of the result is continually at risk during the process of making.
The care counts for more than the judgement.
Much of what is ordinarily called skill is simply knowledge.
There is a strong incentive to design only in terms of shapes which are easy to communicate.
No two leaves of the same tree are precisely alike, each is individual: yet every one of them conforms to a recognizable pattern characteristic of the species.
Design - the music of design - depends on the relationships between distinguishable and separable features of things.
It [workmanship] takes over where design stops.
You must not torture your material.
We can have no direct rapport with the nature of any material, but have to judge what it is by looking at the surface. We can never see the thing, the material itself, but only the surface, which our vision, unlike X-rays, will not penetrate.