Every logic puzzle is a story somebody declined to tell you.
A grid, a dozen labels, and nothing whatever about why these people are in the same building on the same night. I solved those for years before admitting I had never once cared which of them did it. So these books start at the other end. The case arrives as a story, with people in it, and the grid is what you use to settle the argument.
The rest follows from a single rule. A case goes in only if it can be proved. The solution exists before any of the clues do; each clue is built backwards from it, and then every other arrangement of that grid is tested and thrown out. If a second arrangement survives, the case is not deduction, it is taste, and it does not get printed. Nothing in these books rewards a hunch.
A hotel does a great deal of that work unassisted. It puts several hundred strangers under one roof, hands each of them a key and a reason to have been somewhere they were not, and then runs a service corridor behind every room with a door at both ends, so nobody's account of the evening is ever quite as tidy as they would like it to be. Grand hotels also keep paper — a register, a laundry count, a docket for everything that comes in the back — and paper is what turns a suspicion into something you can argue about.
Margo Pike works contested claims for an insurer that covers hotels and very little else. She is not a detective and she solves nothing. She hands over the file and gets out of the way, which is the only honest arrangement in a book where the reader is the one holding the pencil.
Not every case is a death, either. A claims file holds fires, thefts, a forged register, two disappearances and a ledger that went into the lake. That is what makes sixty of them plausible inside one building, and it is why no two of them read the same.
I write from lake country in the north of Idaho — not Lake Superior, but it keeps some of the same hours. Six months a year where leaving is a decision rather than a drive. It is a useful place to think about a building full of people who cannot easily go anywhere.
A different property every volume, and each one stands on its own. Every volume also comes in a large-print edition set at sixteen point, which is the difference between a book somebody finishes and a book somebody shelves.