Having loved Hold the Rein Free, I picked this up at a book sale and didn't realize until I started that this is actually nonfiction, a short collection of vignettes about various horses the author has owned over the years (including but not limited to the three foals born from her very first and apparently-nameless titular gray mare, though all the others have lovely names), while living and working on ranches in California, outside of San Diego.
Aimed at juvenile readers, this is Extremely Horsey almost to the exclusion of all else -- I found myself wishing there was a little more memoir to it, because from what I could glean via googling, she has had a pretty fascinating life but the chronology here is somewhat unclear, with only occasional timeline references to orient yourself, beyond knowing the stories took place circa the late 1920s/early 30s-60s.
But I am also an Extremely Horsey person who never grew out of horse books, so that was actually not a deterrent to me at all and I loved every page, including the numerous black and white sketches peppered throughout. Now I am only more inspired to read more of her books, all of which seem heavily informed by her life and experiences, as well as her actual memoir.