The Midnight Mysteries series contains some of my favorite hidden object games. These are the more typical hybrid type games, that have some adventure elements (puzzles, moving between locations, talking to people) as opposed to the find-objects-only style.
Midnight Mysteries are interesting in that they are based on real historical events, then add some fictional what-ifs to fill in blanks or give alternate explanations for known events. As a result, not only are the fun as a game but they spark some interest in reading about the real events on Wikipedia.
MM4 goes into the death of Harry Houdini and proposes a little mystery, that maybe the accident that sped up his death was actually intentional, and if so, who wanted to kill him.