I just read Bill Buxton’s “Sketching User Experiences” (Morgan Kaufmann 2007). Highly recommended. It has had a significant impact on my thinking of the process of innovation.
Buxton does an excellent job of delineating the role of sketching and leads the reader by example. One key point is that while we all know how sketching is a learned art, improved by practice, the reading and interpretation of sketching is also a learned art.
While the book seems to focus on traditional sketching, it does a very effective job of bringing the reader to understand the nature of “user experiences” and the context of sketching those experiences.
Very enlightening. http://www.amazon.com/Sketching-User-Experiences-Interactive-Technologies/dp/0123740371/ref=sr_1_1?ie=UTF8&s=books&qid=1197241433&sr=1-1