Secret Passages
A conversation takes place in which a boy suggests that females, by nature, are more sensitive than males. "To emotions, yes. To nuances of human behavior. Not necessarily to secret passages in a wall." The boy responds that they are pretty much the same thing. Secret passages are turned into a metaphor intended to convey the idea that emotional nuance is a challenge to understand, but worthwhile as keys to unlocking the hidden mysteries of why people sometimes behave in seemingly inexplicable ways.
Civility
Another confrontation between males and females threatens to erupt from argumentative disagreement into full-fledged violence. Lockwood intervenes before that can happen, telling them both "This is an interview, not a boxing match." Ironically, Lockwood is acting as a referee when he references boxing as a metaphor for civil disagreement threatening to get out of hand.
Setting
Similes are abundant in the plentiful descriptions of the weirder aspects of the novel. For instance, the description of the setting often benefits from the comparative strategy. "The blackness of the landing was a formless space. On my left, white banisters hung at head height like a row of giant teeth." Black formlessness is challenging to convey even through comparison. But everybody can envision the simile of giant teeth which brings the banisters more vividly to mind.
Atmosphere
Both metaphors and similes are often used together to create and sustain an atmosphere of otherworldly menace and bizarre creepiness. "...bookshelves had erupted into walls of flame; trails of racing fire ran like mercury along the floor...The hole itself was a pool of darkness, the object inside it scarcely visible. Behind the veil of webs, I glimpsed its lip-less smile." Metaphorical language is effectively used in this passage to transform what is essentially a bookcase on fire and a hole in the plaster wall into something far more dangerous and threatening.
Apathy
Feelings of apathy, lethargy, indifference, or just plain exasperation are given an inventive metaphorical makeover. "It was one of those moments when a great Don’t Care wave hits you, and you float off on it." The image created by the metaphor used to turn that familiar feeling is tough not to visualize. It is also effective in the way it offers insight into characterization.
