At last, the cycle is complete. The “Neapolitan Novels” of the pseudonymous Italian author Elena Ferrante, a saga of female experience seemingly written in blood, which has taken the international literary world by frontal assault, has now concluded with its fourth installment. You no doubt have an inkling of the story. Two girls, growing up amid the poverty and violence of postwar Naples; two women, making their adulthood in a world of shifting possibilities and ideologies; two friends, locked in a lifelong embrace, sisters, rivals, doppelgängers, opposites. Lenù and Lila: Elena Greco, studious and disciplined, awkward, our narrator; Raffaella Cerullo, willful, tough, incendiary, stunning, her rival, muse, and subject. Around them in their neighborhood are friends, parents, siblings, teachers, shopkeepers, radicals, mad widows, camorristi—supplemented, as the narrative unwinds its length,…