Horse Racing Forum - USA Thoroughbred Races

I admit I have a pretty rudimentary, especially compared to some here, understanding of how breeding decisions are made, tracing pedigrees, and general savvy on bloodlines and breeding. I was wondering if anyone had suggestions of resources (books, websites, anything!) that might be good starting points for learning about this side of the game? It's something I've always been interested in but find the whole thing somewhat overwhelming when trying to hunt down the best resources on my own.

I've heard TVG's Rich Perloff discuss this very subject, and the first book he always recommends is Breeding the Racehorse, by Federico Tesio. It was published in 1958, so it won't cover recent stallions, but it think it's the theories that he discusses that make it a classic.