Sometimes, more than one clue or info item appears. The bottom corners appear dog-eared when there is more to see. It's best to make sure you've seen all the clues that are available. I completed the highest level of difficulty including the mystery without have seen any clues and it wasn't easy at all. The mansion itself is devided into four levels, each with it's own room.
Most rooms contain video clips of the residents themselves.
Some contain clues to solve the mystery and some even include mini-puzzles. As you move around you'll hear your footfalls on the hardwood floor become muffled as you walk over a carpet or the stair creak when going up or down. It's a nice touch. And many rooms contain further period information. Also a nice touch.