Now that I have read the whole series (and absolutely loved it) I wonder what I'd have made of it as a child, because I'm not absolutely certain these are children's books: certainly not Thunderhead. Whilst the books feature Ken, son of ranchers Rob and Nell, Thunderhead's focus is certainly far more on the relationship between mother and father.
Rob and Nell's relationship in Thunderhead is close to disintegration as the horse business is less and less successful. Rob cannot bear to fail, or be questioned. Fortunately their son, Ken does succeed in taming Thunderhead, Flicka's wild colt, but the horse longs to revert to his wild nature, even though Ken hopes he will save the family fortunes by becoming a successful racehorse.
You're left with the conviction that whatever happens with the horse, the underlying tensions and rifts between Nell and Rob are far deeper than anything that can be cured with a horse. It's certainly not the stuff of which the everyday pony story is made.
~ 0 ~
More on Mary O'Hara