Our story is presented from a number of different angles, each subtly shifting our perspective (that is, restricting or enhancing freedom), so that we can only assemble a complete picture through piecing together the little bits we get.
There are two variations of limited omniscient perspective. In the first section, we meet the Berglunds through the perspective of their neighbors. So, for example, we're told that Patty "appeared to be doing some immoderate drinking of her own," judging by the way she looks in the morning when she walks out to get the newspaper (1.1.167) (italics added). When we finally hear from Patty herself, it's through what Patty reports to the other mothers (1.1.28). Much of what we hear comes from Seth and Merrie Paulsen. As Merrie is very politically active, she harps on Patty's apparent lack of any political principles. Seth, meanwhile, seems to have a crush on Patty, so he wonders whether Patty and Walter are still in love (1.1.17). That the Paulsens are "far down on [Patty's] list of go-to neighbors" (1.1.84) reinforces the real distance we have from our subjects and emphasizes just how unreliable all of these "facts" probably are.
Next, there's a rather unconventional narrative form we might call a "Third Person Autobiography," as Patty writes her own personal history, yet refers to herself in the third person in it. One purpose this serves is to give some distance from the events described. Perhaps it allow her to speak more freely about the subject matter, as if she can be totally objective about all of it.
Finally, there are a few more typical examples of limited omniscient perspectives, told from three characters' viewpoints, alternating between Walter, Richard, and Joey. Giving insight into their internal worlds, we find out that these men are not quite as strong and self-assured as they appear from the outside. In Walter's sections, we learn than the supposedly mild-mannered man is actually boiling (and sometimes boiling over) with rage. Joey has learned to almost effortlessly manipulate the world around him, but he has considerably more difficulty controlling himself. And Richard (who in these sections is called "Katz," presenting him as less of a friend and more of an autonomous subject) is continually struggling both with very real addictions and more abstract questions of authenticity.