Criss Cross is written from multiple perspectives that shift throughout the novel—and yes, one part is written from the perspective of a necklace! However, the entire book isn't written from the necklace's perspective.
If you look at the first chapter of the book, called "The Catch," you can determine the perspective by looking closely at whose point of view the narration seems closest to. The first line, "She wished something would happen," suggests that it's a girl. In the second paragraph, the name of that "she" is revealed—Debbie. The reader sees what Debbie sees and hears Debbie's private thoughts, so it's clear that this chapter is told from Debbie's perspective.
But then take a look at the first line of the second chapter, titled "Hector Goes into a Sponge State and Has a Satori":
Meanwhile, in another part of town, Hector's sister, Rowanne, was upstairs in her bedroom, changing her clothes or something. Hector could hear her humming, and the sound of drawers opening and closing.
How do we decide whose perspective we're in now? It might seem at first that we're in Rowanne's perspective, because hers is the first name mentioned. But actually, the story is following Hector most closely because he's the one who's listening to Rowanne. We're hearing with Hector's ears.
If you aren't sure whose perspective each section is in, ask yourself whose thoughts you're hearing, whose eyes are you seeing through, whose ears are you hearing with as you read the narration. That will give you a clue about whose perspective the book has shifted to.