Let's get the downside out of the way first - CosyKiller is a year-long subscription. Telling one story over twelve monthly boxes, it's some commitment of money and time.
What it gives you back for that subscription is unsurpassed in terms of mystery subscription boxes. There are no phone numbers to call that might end up disconnected after a few months, there are no websites to visit that might be taken offline at no notice, everything you need is there in the boxes.
And what boxes they are - one month you might get a 128 page diary/journal containing two obvious ciphers and one very well hidden one. You might get twelve to sixteen letters from one character to another, including drawings and birthday or christmas cards. You might get clay artifacts, or death certificates, or shipping manifests, or telegrams, or....
You can read something in box 8 that reminds you of something in box 1 to find an inconsistency in testimony that feeds into the final solution - you can find ciphers in early boxes that are made more explicit later on, but still solvable at that early stage.
The commitment is huge, but the project is major league, satisfying, intelligent, interesting and thoroughly recommended.
I always fear when a new product has a great launch, I worry that all their ideas have been front loaded and used up and they have nothing left to offer. Having received box 2 yesterday I’m ecstatic to announce that Boxed Locks 2 takes the concept to another level. There’s an interesting narrative....there’s a vast array of different puzzles, ranging from the simple to the hard as nails (and one of which makes you clap when you realise the trick)...there’s an evolution of the hint system should you need it....and there’s a narrative payoff right at the end that’s a beautiful capstone on the experience. Unreservedly recommended.