Horses are born crooked. They are generally left-handed, as in prefer the left lead. Some are just more noticably crooked than others.
People are crooked too. Most of the time, if we work really hard at it (sometimes REALLY hard, which, granted, not everyone has the ability and/or desire to do), we can fix ourselves. But even a crooked rider can learn to straighten a horse, as long as the rider isn’t TOO crooked (and what might be too crooked for one horse might not be for another, depends on the horse).
The book is really, really interesting. I don’t think it’s bringing out any new revelations, but at least for me, it’s putting things out there from a different perspective, and for me, it has really made a difference in how I try to see and feel what my horse is doing.
I have no doubt that good trainers/instructors work on straightening the horse from Day 1. But, as we can all judge from the umpteen million threads hear and on H/J and even Horse Care, there aren’t enough of those good trainers/instructors, there are VASTLY more poor trainers/instructors, and far too many riders are only taught to ride off the reins. That doesn’t fix crooked horses, and it usually makes them worse or creates them.
So, IMVHO, this book is GREAT for another view into a singular problem that exists, a very basic problem, and gives you tools, if not exact instructions (there are some), on what to do. It’s not for a beginner rider. It’s for someone who is either working with a talented instructor/trainer (like I am) or who has enough knowledge, but not quite the right kind, perhaps, to get the concept and be able to apply that concept to trying to fix the horse.