Upon recommendation from Bob Jewett long ago (back in 2006?), I purchased a book on System Sid from Sid Banner. And I have to tell you, it's one of the best books on pool (nevermind 3C) I've ever read. If you get System Sid "down," there isn't a ball anywhere on the table that you can't kick or multi-cushion contact to.
Also, I'd recommend some others, that I'll list below.
3 Cushion Billiard Systems by Sid Banner:
http://amazon.com/Cushion-Billiard-Systems-Secrets-Professional/dp/8879560506
Secrets of Three Cushion Billiards: Doctoral by Darrell Paul Martineau:
(Former website no longer found -- this book is now hard to find, but well worth the effort if you can find a copy! You'll know when you find it, because it's a big spiral-bound red-covered book with black print.)
Professor Q-ball's excellent website on 3-cushion reference:
http://professorqball.com/diamond-systems-secrets/
Hope this is helpful,
-Sean