Then arrange the class so that they are seated in a circle. If the class is especially large you may want to follow the traditional design of a Socratic Seminar where there is a smaller circle in the middle of the room where the discussion takes place and one larger outer circle which listens and records the conversation in the middle. There is a single empty seat in the middle circle so that students from the outer circle can join the conversation in the circle. I personally prefer to have all the students engaged in the discussion circle so I advocate trying to include everyone in the circle.
Choose one student to be the discussion moderator, a volunteer would be best, and give her the book. She can pick the quote to begin the discussion. Whenever the discussion starts to die down have her choose another quote or image to discuss or pass the book around to the other students and have them initiate the discussion. It is important that as the teacher you refrain from entering the discussion as much as possible. The more adamant you are about not talking the more the burden is put on the students to take ownership of the discussion.
Ideally this should keep the class engaged for the full class period. At the end of class take a few minutes, 3-5, to quickly go around the circle and have each student comment on the usefulness of this form of discussion.