Megha Majumdar’s second novel, “A Guardian and a Thief,” a National Book Award finalist in 2025, is a book that makes a thoughtful reader ask what sorts of pleasures they are looking for in their reading. The ones to be gained from investment in this book — and while it is not a long novel, it does take a certain kind of emotional investment — are mostly quiet. They are contemplative. The craft of this novel is something approaching immaculate.