I'd suggest reading Danny Roddy's site and his book, which I think might still be free. A hair-centric approach misses the point.
Danny's book is very interesting. When I first read it, I was like WTF is this? I can't understand anything. Years later I picked it back up and it made more sense. It still holds its own after nearly 7 years. Very professionally written and every time you re-read it, there's more stuff to understand.
His articles since then have been very good too, I strongly recommend them, they're good material to read, and re-read and in particular, explore his references too.