The series as a whole is structured as an epic, I suppose. But each book has its own structure. The first four were detective novels, if you'll forgive some oversimplification (who the bad guy is has been the central question, and we've been able to track clues in the text as we went along). But this one is structured like a tragedy. I am curious to see whether it also has a detective story component. I cannot remember one at the moment.