Epigraphs are like little appetizers to the great main dish of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
"Love is the world's infinite mutability; lies, hatred, murder even, are all knit up in it; it is the inevitable blossoming of its opposites, a magnificent rose smelling faintly of blood."
—Tony Kushner, The Illusion
What's up with the epigraph?
If epigraphs are supposed to set the thematic and emotional tone for a story, this one makes us feel kind of creeped out. For a statement about love, it sure isn't very loving—since when do lies, hatred, and murder play roles in romance? Since Tony Kushner wrote his play The Illusion, the story of a guy who, as part of a search for his estranged son, gets to see three different versions of his life starring three different versions of the same people.
If you're thinking this sounds an awful lot like Nick and Amy's identity issues, you're right—these people withhold information, change their stories, and rewrite history so often that even when the book ends, we're still not totally sure who they really are. We spend most of Part One trying to determine if Nick really is a killer, only to have him become the dude we're rooting for; likewise, we see Amy as the victim, only to discover that she's the real criminal.
What about the whole "love" theme in this epigraph? Kushner's essentially saying here that love is volatile and capable of causing destruction, that as much as it manifests as affection, it also inspires terrible behavior. His definition of love sounds oddly like Go's explanation of Nick's people-pleasing behavior:
"You'd literally lie, cheat, and steal—hell, kill—to convince people that you're a good guy." (7.26)
Whether it's love of approval, like Nick, or love of attention, like Amy, love motivates all kinds of sick behavior. Both these addictions contribute to the dysfunctional Dunne marriage. "We're a sick, toxic Mobius strip, Amy," Nick says near the end of the book. "We weren't ourselves when we fell in love, and when we became ourselves […] we were poison. We complete each other in the nastiest, ugliest possible way" (56.12). If love is a rose, then Nick and Amy's is covered in thorns.