I beta tested this game.
Napier's Cache is in an unusual niche of historical fiction, and is based on a family story of the author.
It is fairly linear in story with nonlinear interactions in each 'phase'. You first have a small treasure hunt, followed by a dinner scene, then another treasure hunt and a simple maze.
In design it reminds me quite a bit of Christminster, an early (pre-IFComp) inform game that was well-regarded at the time, that also had you doing things like eating at a dinner with scholars and discovering the history of old alchemists.
Overall, the quality is well-done, and most reasonable interactions are coded for. I enjoyed each iteration of this better than the previous, and I believe this is something to be proud of.