I played The Addicott Manor on Halloween, and it was a perfect selection: a solo visit to a haunted mansion!
In terms of gameplay, The Addicott Manor is choice-based. The choices are given to you in list form after a piece of text. Then you have to click on the number that corresponds to your choice. With the interface that this game features I suppose this is the only way to do it, but it feels a little more immersive to me to click on my choice itself than on a number that corresponds to that choice.
The title page tells you that there are six treasures. I played through several times, but I never did better than escaping the house with two of the treasures. This is a game with a good bit of replay value.
Overall, The Addicott Manor worked for me in terms of creating that horror vibe of slowly exploring a sinister, ominous mansion. I could feel my pulse rising a little while I played. And I wanted to find the treasures: I kept playing and playing until I had achieved a small measure of success.
A few minor critiques: There is a lot of text at the beginning, which made it a bit hard for me to get into the game at first. Once I got into the mansion the ratio of text-to-choices worked better for me, though. There are a few too many grammar mistakes; more proofreading would have helped. Also, occasionally the game presents a choice to you that's actually unavailable. This may be a function of the program used to create the game, but it would have felt more immersive for the game to list only those actions that are actually available.
Fun fact: The PC drives a Ford Fiesta, making this one of three games in IFComp 2018 to feature a character who drives a Ford Fiesta.