I've been pleasantly surprised at the extent to which my book, Raising Purity: Nurturing the Image of God in the Heart of Your Child, has resonated with singles. As the title suggests, it's marketed toward parents. But at it's core, the book is really a theological, biblical, and practical look at the issue of purity, so the application is pretty broad. I've used it as the primary text for a number of workshops I've done for single adults, and the response has been strongly positive. A few chapters discuss the ways in which our contemporary dating/courting practices have potential to bypass some of the assumed ethical norms of the New Testament understanding of purity, and I think these chapters in particular have struck a chord with single adults.
If you're single and you've read the book, I'd be interested in your feedback.