Depth of the Rain by Orin Drake - Free

Two worlds collide, bringing an outsider home, and the rest of existence to its knees, in a manner of speaking. A teen -aged girl who has been called Shadow from modern human Earth gets pulled into another world, and hurled into a quest she has no idea how to pursue. She meets up with a brother and sister from the other world, a horse who understands every word they say, and a very disturbed boy that may or may not really be helping them to achieve their goal. Their destinies are intertwined.