One sentence: loving couple does mystery investigation during a magic-driven industrial age

Things I enjoyed about the book:

• established caring relationship between two very different people, who understand each other's quirks and needs (reminds me some of MRK's Glamourist Histories)
• investigators who aren't cops (and are also anti-royalist)
• setup for future books, but not in a way that detracted from this one
• interesting magic system that also has social implications
• an industrial age powered by fuel from portals to a hell dimension (and requiring people to fight back monsters trying to come back through said portals)

I know "romp" is overused as a fiction description, but this is a romp if ever I've seen one. It's grippy action scenes and compelling characters, but more than that a romp for me is fiction that calvinballs its way to undiscussed locations or adding new worldbuilding details with very little foreshadowing. I think this can be done poorly in a way that feels shallow or disconnecting, but here I was entertained and compelled.