Shadow Rider by Christine Feehan

 This was my first time to try reading Feehan's books - she seems to have published a ton. The concept of Shadow Riders, as introduced in the early going, seemed intriguing, so I pressed on, hoping to find out more about their mission, find out why the heroine was "fated" to be with the hero, and if she had any cool powers, and so forth. Halfway through the book, it descended completely into over-the-top porn, and I gave up on actually finding a plot or coherent story. Plot's evidently not why people buy Feehan's books.