Wow. This was a lot (in a good way!). Some observations:
I loved the feeling of walking through a mansion, looking at clues and talking to suspects. The mansion was nicely detailed: all the rooms you'd want in a mansion, doors everywhere, windows and portraits and plants and furniture to make it feel complete. And I liked the way some clues were incomplete and needed more investigation (in my run, I found some cigarette ashes in a room, and had to separately find the suspect who smoked cigarettes).
The thing I think it needed the most was a map: I had trouble in some places even figuring out where I'd already been, and the note telling me that so-and-so was in the study only helped if I could find the study again!
(The game occasionally lagged--froze up, did nothing, and then woke up a few seconds later--but that might have been my computer and not the game.)
Overall, this is really cool!