This unusual novel is somewhat experimental in form, with short chapters that read like diary entries, in a powerful first-person voice from a somewhat unreliable narrator. It is the unreliability of that narrator, as well as the compelling background of her character, that really informs the trajectory of the plot. Therefore, some of this novel's most significant quotes are related to the revelations of the character's past and the moments when her honesty and reliability are called into question.

Certainly, the novel's opening lines are important, as they firmly establish the tone and style, introduce the main characters, and give a sense of the forthcoming story. It should also be noted that before the novel's text appears in the book, there is a hand-drawn map of the main setting (Beechwood Island) and a chart depicting the Sinclair family tree. The family background is significant because the family's wealth and privilege—and the disintegration of both over time—are crucial elements in the plot. The novel's very brief first chapter beautifully portrays the novel's spare yet lyrical style and the unique, intimate voice of its narrator:

WELCOME TO THE beautiful Sinclair family. No one is a criminal.

No one is an addict.

No one is a failure.

The Sinclairs are athletic, tall, and handsome. We are old-money Democrats. Our smiles are wide, our chins square, and our tennis serves aggressive.

It doesn’t matter if divorce shreds the muscles of our hearts so that they will hardly beat without a struggle. It doesn’t matter if trust-fund money is running out; if credit card bills go unpaid on the kitchen counter. It doesn’t matter if there’s a cluster of pill bottles on the bedside table.

It doesn’t matter if one of us is desperately, desperately in love. So much

in love

that equally desperate measures

must be taken.

We are Sinclairs.

No one is needy.

No one is wrong.

We live, at least in the summertime, on a private island off the coast of Massachusetts. Perhaps that is all you need to know.

We see here not only a description of the narrator's emotional state but also an indication that the novel will unfold in the present tense, albeit with a strong sense of the recent and occasionally distant past. The formatting of some lines as fragments gives this the look of poetry, and it is possibly a stream-of-consciousness approach.

The "accident" is something referred to frequently. It is an accident that changes the narrator (Cadence, also known as Cady) profoundly and that informs her actions, thoughts, and physical well-being for years afterward. It occurred during the year known as "Summer Fifteen" on the island where her family spends the summer, and Cadence spends a fair amount of time rehashing the events of Summer Fifteen. In chapter 28, Cadence tries to unlock some of the mysteries surrounding the accident and engages in a form of self-inventory and detective work to get answers. The passage where she does this explores the most significant aspects of the accident, its causes, and its impact on her life:

A PAD IS left from several summers ago when Gat and I got obsessed with graph paper. We made drawing after drawing on it by filling in the tiny squares with colored pencil to make pixelated portraits.

I find a pen and write down all my memories of summer fifteen.

The s’mores, the swim. The attic, the interruption.

Mirren’s hand, her chipped gold nail polish, holding a jug of gas for the motorboats.

Mummy, her face tight, asking, “The black pearls?”

Johnny’s feet, running down the stairs from Clairmont to the boathouse.

Granddad, holding on to a tree, his face lit by the glow of a bonfire.

And all four of us Liars, laughing so hard we felt dizzy and sick.

I make a separate page for the accident itself. What Mummy’s told me and what I guess. I must have gone swimming on the tiny beach alone. I hit my head on a rock. I must have struggled back to shore. Aunt Bess and Mummy gave me tea. I was diagnosed with hypothermia, respiratory problems, and a brain injury that never showed on the scans.

I tack the pages to the wall above my bed. I add sticky notes with questions.

Why did I go into the water alone at night?

Where were my clothes?

Did I really have a head injury from the swim, or did something else happen? Could someone have hit me earlier? Was I the victim of some crime? And what happened between me and Gat? Did we argue? Did I wrong him?

Did he stop loving me and go back to Raquel?

I resolve that everything I learn in the next four weeks will go above my Windemere bed. I will sleep beneath the notes and study them every morning. Maybe a picture will emerge from the pixels.

This passage not only outlines all of Cadence's questions and worries but also indicates her resolve to continue to unravel what happened. This will inform the chapters that follow as they trace the occurrences of Summer Eighteen, which is the "present" period that the novel takes place in.