A Delightful experience
I ordered the KiY kit for my brother and Mom a few years ago, and I absolutely loved it. My brother is not much of a horror fan, and my mom didn't fully realize what was happening, but I was so excited.
The final package is truly beautifully designed, and I actually still wear the pendant to this day(seriously it has held up for 3-4 years of wear and still looks great.) I also ended up taking the statue for myself since my brother was pretty freaked out by it, and when I returned home on vacation it was hidden in the garage, so I took it.
My one note on the system is to be aware who you are sending it to. I had expected more of a puzzle based experience, rather than an incrementally developed story. My mom loves puzzles so I thought of them, but when the first instalment arrived they thought someone had sent them the letter by mistake and lost the papers in a drawer somewhere...
During the experience, I read the "King In Yellow" by Robert Chambers out of curiosity and absolutely loved it. When the final package arrived, I got chills.
I believe it would add to the experience if the final package included a copy of the book, or at least a few tales from it. But if you plan on gifting this to someone, you might also consider sending them a copy as well.
That said, the presentation, items, and overall quality of the packages are amazing, and I would absolutely order it again.