In his own words:
In writing this novel, there were a few challenges, though the actual work proceeded more smoothly than it had in previous novels. In some ways, the story seemed almost inspired, for lack of a better word, and I not only enjoyed the writing process, but there were times when I was surprised by the turns the story took.
The major challenge of the novel regarded the blending of spirituality into the text. Though faith is a powerful element of my own life, when I set out to write a novel, I am guided by the simple thought of writing a story that most people will enjoy. Since religion and faith vary greatly among my readers, it was difficult to write such a story with a balance that wouldn't offend anyone. Nor did I want to preach to anyone. That's not the purpose of a novel.
The reason I wanted to include a spiritual element in the book was simple: This was a story of the beauty, power and innocence of first love. The characters were young and on a personal level (one defined by my own morals and values), I wanted these two kids to be deeply in love, yet without the intimacy that normally accompanies such deep love. In other words, I didn't want them to engage in pre-marital sex, and though my other novels have included that element (I do write love stories), had I done that with two young people, a great many readers would have been offended.
That was also the reason I set the novel in the 1950s. I always want my novels to be believable, and back then, things were different. I don't suppose you need me to go into that, though.
I also wanted the novel to show the power of faith. Ironically, in setting out to write about first love (which I did), I created a strong redemptive element in the novel. I suppose that came from Jamie's faith, and though it wasn't intended, I think by the end, redemption was one of the more powerful elements of the novel.