"A successful relief carving relies not just on the artist's ability to carve the wood, but also on the ability to make use of light and shadow to create depth. This step-by-step guide explores both of these key elements and uses start-to-finish instructions, photographs, and detailed captions to explain what traits make a good relief carving. Also included are illustrations and exercises that reinforce the importance of light in relief, practice exercises to improve carving skills, and patterns for five additional relief projects."
I'm not a wood carver, but I am a sculptor and this book had some gorgeous work in it. Very inspiring, and I learned quite a bit about using shadows and perspective. Still need to work through the exercises, I think that will be valuable.