Let's see, it's hard to recommend novels because everyone's tastes are different.
But I'm not the only one who likes, Jane Smiley's Horse Heaven
is very good. Not scary, lots of English-riding disciplines. It's not a new gifty hardcover, though, because it's been out for a while.
In non-fiction, the newish The Soul of a Horse
by Joe Camp (yes, Benji's trainer). He's an advocate of barefoot horses, but his journey with natural horsemanship (specifically Join-Up) makes for a nice read.
And for something completely different, the book and card set The Way of the Horse
by Linda Kohanov looks like a taro card set but isn't. She's the Tao of Equus
lady who came up with these cards and the book that goes with them that explores and explains the human/equine connection. The paintings on the cards are both gorgeous and compelling. And the book covers a lot of horses in myth and how they enhance human nature.
Anyway, there's a lot of great stuff out there, so it all depends upon what you like to read.