Sibling rivalry runs in the family—a prequel to A Guide for the Perplexed.

In 1980, Jacqueline Luria, the first female physics doctoral candidate in her university’s history, has emerged from her ultra-Orthodox upbringing into a secular world where she tries to untangle the origins of the universe. Then she meets Roger Ashkenazi, a mathematician studying fractals and starting to question his own atheist ideas. Their insights into the world’s repeating patterns cannot prepare them for the coming disaster of their marriage—or its impact on their daughters, one an average child and the other a genuine genius. The rivalry between Judith Ashkenazi and her wildly successful sister Josie, who invents a software program to catalog every kind of memory, will fuel the page-turning plot of Dara Horn’s critically acclaimed novel A Guide for the Perplexed.

“String Theory” takes its readers to the farthest edges of knowledge and the limits of freedom, on a journey from doubt to faith and back again. In its double helix of free will and fate, it anticipates the terrifying consequences, borne out in A Guide for the Perplexed, of asking children to fulfill their parents’ dreams.