Over the (few) years of my writing career, I've had something hammered home in my brain: "Always have a good opening line."
The opening line of the book is the "welcome to my world" that will hook your readers--or not. A good opening line will immediately make your readers want to find out more. A lame opening line won't necessarily cause readers to turn away from your book, but it doesn't instantly hook them. Anything that doesn't arrest your reader's attention RIGHT OFF THE BAT gives them a chance they'll say, "Meh" and close the book.
Here are a few GREAT opening lines:
Call me Ishmael. —Herman Melville, Moby-Dick (1851) (classic!)
A screaming comes across the sky. —Thomas Pynchon, Gravity's Rainbow (1973)
Happy families are all alike; every unhappy family is unhappy in its own way. —Leo Tolstoy, Anna Karenina (1877; trans. Constance Garnett)
It was a bright cold day in April, and the clocks were striking thirteen. —George Orwell, 1984 (1949)
Many years later, as he faced the firing squad, Colonel Aureliano Buendía was to remember that distant afternoon when his father took him to discover ice. —Gabriel García Márquez, One Hundred Years of Solitude (1967; trans. Gregory Rabassa)
Whether I shall turn out to be the hero of my own life, or whether that station will be held by anybody else, these pages must show. —Charles Dickens, David Copperfield (1850)
Whatever you may think of the rest of these stories, you can't help but admit that these are AMAZING opening lines.
I've tried to make my opening lines as "catchy" as possible:
Eyes the color of night watched Lord Damuria plunge to the forest floor. -- The Last Bucelarii (Book 1): Blade of the Destroyer.
I left my city in ashes. -- The Last Bucelarii (Book 2): Lament of the Fallen -- coming soon
Fire and agony filled the Hunter's world. -- The Last Bucelarii (Book 3): Gateway to the Past
The Hunter danced on empty air. -- The Last Bucelarii (Book 4): Anamnesis (working title)
Viola huddled in darkness, shivering, arms wrapped around her knees. Sobs and whimpers echoed in the close, stale air. -- Child of the Night Guild (secret side project)
These lines are all meant to "hook" readers and intrigue them enough that they'll want to find out more.
Unfortunately, this is something a lot of writers are failing to do these days. For example, here is the opening line from an (indie) book I recently read:
The medical examiner's shoes reverberated on the metal floors of the operating room as he walked back to the gurney and stood over the patient.
Not much more than setting there. Why do the shoes, metal floors, or gurney matter? Yes, the patient could be infected with a virus, or the operating room could be on a spaceship. But none of the truly fascinating details of the story or even setting are presented in this opening line.
Later in the same paragraph, it says, "She (the dead body in the gurney) would have almost looked attractive, Jasper thought to himself, had it not been for the pale, grayish tint that had overtaken her skin and the deep Y-shaped incision that the surgeon was cutting into her chest."
Imagine if the author had started the book with something along the lines of "Though he hated to admit it, Jasper couldn't help but find himself attracted to the dead woman on his gurney." Now THAT would have made for an intriguing (WEIRD) opening.
That opening line really has to sink its teeth into you in order to make you keep reading. A good opening line can set the tone for the rest of the book, but a bad opening line can make you cringe. I know which I prefer!