Leah Hager Cohen’s seventh novel, “To & Fro,” is a literary jewel with multiple facets. Its two storylines form a satisfying jigsaw puzzle of cleverly interlocking parts, yet these separate narratives, each following a young girl in search of something she can’t quite define, are also profoundly mysterious, charged with the conviction that many aspects of life cannot — and should not — be explained. Cohen sends both her protagonists on odysseys that lead not to conclusions but to “Two Beginnings and No End.”
