This is one of the best - if you're a fan of espionage AND fantasy/sci-fi, you're going to love this too.
I want to see more of this setting. The REVEAL at the end (no, literally - if you achieve a perfect score, you have access to a command that describes the game's biggest twist and explains the "perfect" ending) left me speechless and also wanting more.
One of the game's biggest puzzles is simply leaving no trace that you were ever there to begin with. This sounds like it'd be a real chore, but it actually required me to be 100% engaged at all times so that I could remember how I had entered the mansion and what I had disturbed. It also allows the authors to completely avoid one of the tropes that is my biggest pet peeve with interactive fiction: you're not forced to be a pack rat... in fact, there are a lot of items that you conceivably could pick up and take with you but are prohibited from doing so because they'll leave traces that you could not clean up. So clever, and I appreciate it so much!