I've never heard of this "method"...off to google!
It isn't really a method, but a way of thinking about getting pregnant. i.e.: the sperm should be there before the egg is popped out. Rather than saying "Oh, I ovulated, I better go put some sperm in."
Basically, it's trying to have sex in the days leading up to ovulation rather than just on the day of ovulation itself.
ETA: I haven't read the book, but that's what the term means...fairly common term on some other boards I frequent.