Series Planning: Building Multi-Book Arcs That Keep Readers Hooked When readers finish a book and immediately scramble for the next installment, you know the author has done something right. Series planning is one of the most powerful tools a writer can master. Whether you’re building an epic fantasy, a mystery series, or a romance saga, the way you structure your multi-book arcs can mean the difference between a forgettable series and one that readers recommend for years.