What is the author's tone in the novel, Underground Airlines?

Victor’s narrative is delivered, for the most part, very directly to the reader. He is an investigator and person of logic and reason, hence he narrates his actions carefully and calmly to the reader, usually without any strong emotion. However, Victor’s sense of humor – a dark, gallows sense of humor – is evident at a few times throughout the novel, especially when he offers sarcastic remarks about legal slavery being "non-violent" (8) and himself as a "mechanism" (6) and not an actual person.