Rate the book from 1 - 5 and explain why you give the book this rating!
1 being lame like my star wars tee shirts and 5 being awesome like your math video's!
Consider things like characters, emotions, engagement, and realism.
Once you have made your statement being dialogue with 2 other students and ask questions about their post. Asking how they felt about characters and the final conclusion of the story.
Finding students that have different ratings will be a good place to get dialogue flowing.