Constructive questions for a book discussion group should ask members with which characters they identify, how they feel about the events of different chapters and what they think the message of the book is. The questions should engage critical thinking skills and encourage members to connect with the book.
One way to promote positive and active discussion in a book group is to pose open-ended questions to the members and questions that help each member make a connection to the book. Asking about a member's least and most favorite character and why she picks those characters helps the member to explore personal feelings about the book. In many cases, the reasons a member provides to support her choices may resonate with other members, growing the discussion further. Alternately, some members may disagree with her reasons and then provide counter examples to refute her claims.
Other questions to ask in a book group should highlight the major events of the book and the ramifications that have for each character and the narrative as a whole. Always include the word "why" in the question to avoid terse answers that don't go anywhere. For example, if a character dies in the book, ask members why the death is important or insignificant to the plot. This evokes more complex thinking than simply stating that it does or doesn't matter.