Answer: gradually
Step-by-step explanation:
Lee Child explains that in order to create suspense, writers need to reveal details gradually, so the readers are left wanting more and are encouraged to keep reading. He explains that even if this strategy might seem too simple, even cheap and meretricious, it´s helpful and effective. While sympathetic characters, elaborate entanglements, and desperate situations are quite engaging for the reader, there´s nothing more effective than the slow unveiling of the final answer.