Sunset Towers is unusual because the people who live in it were hand-selected.
There are many unusual things about Sunset Towers. The fact that each inhabitant was hand picked to lI've there (except the imposter) is only one strange thing. The placement of the building is odd. It is next to the lake, but right in sight of the Westing Mansion. This is no coincidence. Someone wants them to look up, or wants to look down.
Then there's the building.
The sun sets in the west (just about everyone knows that), but Sunset Towers faced east. Strange! (Ch.1)
The strangeness continues! There is one way glass. The features and location are way too luxurious for the cheap rent. No one ever eats at the Chinese place!
Not only do odd things keep happening, such as bombs going off, but the residents get paired up to play the Westing Game. They are all supposedly connected to Westing. The choosing them to live there was no coincidence, and neither was the elderly delivery man.
Soon, of course, it's revealed by the brilliant and misunderstood Turtle that Westing was not only not dead, but actually among them from the start. The whole thing was a convoluted opportunity to reclaim his youth, grieve for his daughter, get back at his ex-wife, find an heir, prove he wasn't dead, come back to civilization, and have some fun.
The odd features of Sunset Towers are all clues, from where it faces where it is located. This is a mystery, after all. Pay attention to anything odd or our of place!