Samantha is just that sort of girl--her father is a horse trainer, and she's been riding all her life, dreaming of being the first African American to compete in the Olympics (her mom's African American, her father mostly Dutch). Her mom is more interested in the family genealogy than in horses; Sam is more interested in the ancestry of her own beloved horse than she is in her own....
Sam is about to get a chance to learn more about her horse's geneaology (and her own) than she could ever have dreamt. For when Sam and her Dad head down to Mississippi on horse business one weekend, Sam falls asleep in her bedroom of the old plantation house they're staying in, and slips through time, back to 1863.
And Caroline, another horse loving tomboy who's the daughter of the plantation owner back in the past, comes into her room to find Sam asleep on her bed. And assumes she's a slave.
Happily, Sam's phone still works (though not as a phone!) back in the past...and it comes in useful when convincing Caroline that she's not, in fact, a slave, but a time traveler. And happily Caroline is both open-minded and willing to confront her prejudices, and glad to meet another horse girl. Caroline and Sam agree that Sam should take on the role of her maid, and they become friends.
But Union soldiers are advancing on this part of Mississippi, and they need horses. Caroline's beloved mare is at risk--and without her, Sam's own horse might never exist. Even more pressingly, Sam herself might never exist in her own time if the slave catcher who's after her has his way....
It's a good story, gradually increasing in tension as both the Civil War and the reality of slavery impinge more and more dangerously on the lives of the two girls. The bond of horse love between the girls helps gloss over the suspension of disbelief required to swallow Caroline's quick acceptance of Sam (Caroline is not exactly the most realistic product of 1863 Mississippi I've encountered, but she has to be on Sam's side right from the beginning to make the story work). Both Sam and Caroline have a lot of learning to do, rather quickly, about the evils and human consequences of slavery, and happily Caroline doesn't get set up as a "white savior," -- both girls have equal agency, perhaps Sam even more. That being said, I would really have liked Pearl, the actual enslaved girl who helps them, to be more deeply characterized--Sam and Caroline are so caught up in each other that they don't spend quite as much time as I would have liked thinking of her as a real person (but goodness knows this is pretty true to form for young teenaged girls who are caught up in a close friendship).
In any event, if you have a horse girl on hand, who might be ready for a change from cantering around in the present, this is a fine book to offer her (and she might well already be a fan of Maggie Dana's Timber Ridge stories of horse girls in the present). And it gets bonus Time Travelling points from me for the clever and entertaining use of Sam's phone!
(I love the picture of Sam on the cover of the book! It really captures her character. Poor Caroline doesn't come off as well--but of course she hates having to be all dressed up, as she is here!)
disclaimer: review copy received from the author