Honestly, I think the best novel from Adrian Graye has to be 'The Unseen Guest.' It’s not his most popular, but the way it blends a historical setting with these creeping psychological horror elements really got under my skin. I read it years ago and still think about that ending sequence in the old mansion. People often recommend 'Whispers of Dust,' and while it’s good, it feels a bit more conventional to me.
That said, if you’re looking for where to start, 'The Chronicler’s Mosaic' is probably the safer bet. It’s more accessible and has a wider cast of characters you can latch onto. But for pure, unsettling atmosphere and a protagonist whose unreliability you genuinely question, 'The Unseen Guest' is the one I keep going back to.