It's not just Gamache. Supporting characters like Ruth Zardo, the bitter old poet, have arcs that span the entire series. Her first appearance in 'Still Life' is a caricature; by book ten, she's a profoundly complex figure. If you met her mid-arc, you'd either hate her without context or miss the tragedy of her development.
Penny treats every resident with that level of care. So yes, order matters immensely.
Consider the 'Armand Gamache' series as one very long, excellent novel. Each published book is a volume. You wouldn't read volume seven of a novel first. The analogy holds perfectly. The continuity of relationships, rivalries, and personal history is that dense and interconnected.
I have a friend who read 'All the Devils Are Here' (book 16) first because it's set in Paris and she liked the setting. She enjoyed it but said she felt like she was missing an inside joke the whole time. That's exactly it—the series becomes a collection of inside jokes, callbacks, and emotional shorthand for longtime readers. Order grants you membership.
Can we talk about the setting for a second? Three Pines feels so real. The order of the books also tracks the seasons in the village, which Penny describes beautifully. You get used to the rhythm of life there. That's another reason to go in order—it's like visiting a favorite place year after year and watching it change.
Hmm, I think I've only read a couple of these. My mom loves them though. She's always talking about Three Pines and Inspector Gamache. I know the first one is 'Still Life'. The last one she mentioned was 'A World of Curiosities'. Not sure about all the ones in between, sorry. I should probably borrow her copies someday.