I've read Doors of the Sea by David Bentley Hart. I am having trouble understanding his point on suffering?

He is a very intellectual man first off. He makes examples using Ivan's conversation with Alyosha and with Voltaire's point of view. St. Thomas Aquinas I understood clearly about Primary causality. However, I am overlooking a major point because toward the end of the book I discovered a lot of emphasis on creation. Please help! I want to thoroughly understand Hart's view of suffering. There are bits and parts but he goes round and round in my perception. Obviously, I am missing a major point.