"I blink rapidly, and the dark spots disappear, but the world still swims around me, like I am tilting forward and back in a rocking chair."
Tris experiences this floating sensation immediately upon being injected with peace serum in Amity, and this choice of simile is specific enough to clue readers in to exactly what the serum feels like. Just like with all serums and simulations, the most notable difference between the serum and reality is the feeling of a lack of control. Normally this would infuriate Tris, and once the effects wear off she is angry—however, there is a part of her that appreciates the feeling of bliss that the peace serum brought on, since it is not something she ever really gets to feel naturally.
"The vibration feels like a sigh going through my body."
Tris's first narrow escape from danger occurs as she and her group run from Amity, from the Erudite and Dauntless traitors who came to search for them. When she gets on the train, she compares its vibration to a sigh; the choice of the word "sigh" in this simile emphasizes the relief she feels after having gotten away. Throughout this novel, there will be many similar moments of relief after a risky situation—however, Tris can never really feel true relief, since there is always a greater challenge on the horizon.
"Then the chair hits the ground, shattering like a brittle skeleton."
After being forced to reveal the truth about Will's death while under truth serum, Tris gets angry and throws a chair off the ledge of the Merciless Mart, using this simile to describe what it looks like when it falls. It is no coincidence that she chose to compare the chair to a brittle skeleton; death is constantly on her mind throughout this novel. This also leads into a brief contemplation of her own suicide, and she wonders what it would be like if she were that brittle skeleton shattering on the ground.
"Sometimes i feel like I am collecting all the lessons that each faction has to teach me, and storing them in my mind like a guidebook for moving through the world."
This particular simile illustrates the lessons that Tris has learned from her experiences with each faction, lessons that citizens who spend their entire lives exposed only to a single faction do not get to learn. This is another flaw in the faction system; each faction has so much to teach the others about their particular virtue and their lifestyle, yet they have been so long separated from each other by faction boundaries and oaths of loyalty that these lessons have not had a chance to spread.
"Jeanine's eyes turn into glass."
This metaphor is used the moment Jeanine dies after Tori shoots her. It is notable not only because Jeanine has died, but also because of the choice of the word "glass." Glass is fragile and easily shattered, and comparing Jeanine to something like glass emphasizes Jeanine's own fragility, too. She put on a facade of strength and impenetrability, but now at last, she has broken—just like glass.
