Third Person (Omniscient) is the perfect point of view (POV) for a complex murder mystery like this one. We actually can't think of anything else that would work better. This POV allows Raskin to represent the thoughts of each character at any time, while also revealing more to the reader than any knowledge that's given to one single character. For example, all the characters share their clues with the reader, even though they won't share them with other characters necessarily. Watch, though, how some characters only say what their clues are at specific times, so the reader doesn't learn too much too soon. While we as readers are like privileged characters, the narrator is still keeping some elements of the game from us.
Lots of detective stories or mysteries focus on one single character for POV, usually the person solving the mystery. Here, since everyone is working to solve the puzzle, it makes sense to weave in and out of each person's consciousness while never getting bogged down in any one character. This narrative voice definitely knows more than the other characters; consider how it tells us at the beginning that one of the tenants is a mistake, for example.