I've got one by Ken Perlman which really helped me. It's Mel Bay's "Basic Clawhammer Banjo." But it isn't really basic. I also bought Songster Bob Clayton's book, and it's really good especially for a beginner. His is the first explanation of clawhammer picking that made any sense to me.

Count me as a banjo player and builder too (or at least a wannabe on both points).