The appeal of books will elicit information you need from the patron to appropriately suggest books that match their needs and interests.
Genre: Does the patron enjoy mysteries, biographies, or romance novels?
Setting: Where is the story set? One city or around the world? Outdoors?
Time: When is the story taking place? Past, present, future?
Length: Does the patron like short stories or epic novels?
Hero: Is the main character innocent or sophisticated? Is there one hero or many?
Plot: Does the story have a point? Is there a definite beginning and end?
Pacing: Does the author move the story with action or dialogue?
Subject: What or who is the book ultimately about?