I voted The Black beacause I have every Black Stallion, Island Stallion and horse book Walter Farley wrote! I loved his book Man'o War, and I still cry when I read it. (yes I still read those books and you can't stop me!)
I was wondering if anyone read any of the Marguerite Henry books? King of the Wind, Misty of Chinncotaugue (sp?), loads more of those too. The Christine Pullein-Thompson books taught me a ton about the UK! My grandmother made soooooo much more sense after them!
By far my favorite horse book? King of the Wind by M. Henry, all about Arabs and wow!!! If you haven't read it please please try to find it and do so. She is a great writer. It is a little young but hey that just means you will be done in no time!
I am a HUGE reader and horse were a HUGE factor in that. While I didn't have one I could read and use my imagination about them. When I did have one I could learn stuff and try it out myself! (not actually a great practice, but hey I was a kid!)
As I got older, this is kind of silly

, I would buy any book that remotely had horse or equine related stuff in the title and boy was I surprised to read books that weren't about horses so much, but turned out to still be really good!
Sheri