Scribner: 259 pp., $25
Fairy tales are the Euclidian geometry of fiction. Reading them — and having them read to us — are the moments when we first divide reality. We teach our imagination to leap, hit the ground and keep on running. We willingly take that leap — children, adults and everyone between carrying that tiny grain of disbelief in the "real" world of facts and plunge instead into a world of fables.
So Monica Ali's "Untold Story," a novel of "what if," will come as no surprise. It is based on the idea that Princess Diana staged her own death and ran away, most painfully from her two...