Reading The Osiris Ritual demonstrated to me that I liked Mann's first book, The Affinity Bridge, more for the novelty of a steampunk detective team than for the writing itself. He clearly has a lot of talent, and loves his characters, but it doesn't seem like he spends enough time getting to know them - they all come across as rather flat. It doesn't take more than a couple of pages to tell me that a) Newbury is very smart, b) Newbury is addicted to opium, c) Newbury is attracted to Hobbes, and d) Hobbes is a woman. That's first chapter stuff, but nothing had really been added to that list by the conclusion of the book. In the end, The Osiris Ritual, like Mann's first book, is good for a light, quick read, but it left me wanting something more substantial.
That said, if you're looking for a fun book that has zepplins, clockwork men, and plucky Victorian ladies, and doesn't spend too much time dwelling on the negative consequences of industrialization, Mann's books are a great choice. Think of it as beach reading for the steampunk set.