Why did you dedicate Spectacular Sins to Joseph?
The book is about taking spectacular sins and seeing how they are used by God—ordained by God—to bring glory to his Son. One of the clearest stories in the Bible that most people who are biblically literate know about is the story of Joseph.
The sin that I have in mind with Joseph is that of his brothers when they sold him into slavery after they almost killed him, lied to his father about what they did, created the impression in his father that he was dead and eaten by an animal, and were gleefully cavalier about the destruction of his life.
All the while the Bible says, "God was sending him to Egypt."
Thirteen years later the point of the story emerges after poor Joseph has been mistreated by the slaveholders, lied about by Potiphar's wife, refused to be remembered by the cupbearer when he was sent back to the king, and his life was miserable for all those years. All the while he was being loved and used by God for the rescue of the people of God.
So Joseph—probably more extensively in the Bible than any other character—is one whose story is to make the point, "You [brothers] meant it for evil, but God meant it for good."
Now that's what this book is about. And the key is that Genesis says, "You meant..." but it doesn't say, "God used...." Rather, it says, "You meant it for evil and God meant it for good," which means that God had a meaning in your meaning, and through your action God had an action. And the book is about how God ordains and causes sin to have a certain redeeming effect.
So Joseph becomes kind of the paradigm in the Bible for what the whole book is about. And that is why I think it is a helpful dedication.