'Walking Bass-lines for Guitar' by Jean-Marc Pillard (Mel Bay).
I've been working at the 'walking while comping' style recently, and this looks like a really good, systematic approach for developing it. It's all based on bass lines harmonised with two-note diads on top, but it should be relatively straightforward to extend the chordal aspect once I'm more comfortable with it. Of course, it's all written for six string, but I'm going to start adapting it for the seven as soon as possible!
Mel Bay has a bit of a bad reputation, but their jazz resources are mostly excellent as far as I've seen.
I'll post back with progress and observations...