Nathan Bransford posted a while ago on how prologues in books can be problematic. The main idea is that they are often unnecessary and require the reader to essentially "start a book twice." It's worth reading if you're considering starting your novel with one.
Soon after reading that post, I picked up my roommate's copy of Pillars of the Earth, by Ken Follett. As irony would dictate, I opened it up and stumbled upon an absolutely amazing prologue. Seriously, this was the type of passage that makes you close the book momentarily to let your heartbeat slow down, after which you check the clock and convince yourself that nobody will notice if you get to work just a liiittle bit later than usual.
Since I was already in "prologue mode" after Nathan's post, I started thinking about why this one worked so well. For the purposes of this post, I've summarized the prologue below. If you have time though, I'd recommend reading the entire prologue on Follett's webpage here, if only because it's a good read.
The prologue starts with medieval peasants gathering for a hanging. We soon realize that there's something strange about this execution -- the accused is a foreigner and has no apparent motive for the crime. There's the normal heckling as he gets positioned on the gallows, but then he starts singing. His voice is strong and beautiful, and he is clearly singing to someone in the crowd. The mob parts to reveal a young woman, weeping silently and pregnant with the accused's child. After this brief, magical moment, the execution continues and the ox pulls away. The man hangs. However, there's a twist -- a bystander's scream draws our attention back to the young woman, who has dropped to her knees. She delivers a curse, calling down suffering and death on the three witnesses who had unjustly condemned her lover. She seals the curse by beheading a cockerel and splattering the blood on the accusers. The scene ends with her fleeing into the forest while the three dazed accusers watch the headless rooster run in circles under the body of the executed man.
I had stumbled on this book casually, not really intending to read the whole thing, but after the prologue, I was hooked. Why is this prologue so effective?
1. It pulls you in
Follett sets up one of the most gripping and emotional scenes I've read in recent memory. It's even more impressive when you realize he does it with characters the reader has known for a total of 2 pages! This is the challenge of a prologue -- to make the reader care right from the beginning. There are several factors contributing to how he accomplishes this goal, including his vivid imagery and use of emotional themes that are engaging even with unfamiliar characters. While intensity isn't a requirement -- there's probably some nice unemotional, calm, but still effective prologues out there -- the intensity of this one sure helped a lot.
2. It ends with a hook.
As Nathan mentioned, prologues make the reader do the work of starting a book twice. The solution? Make her actually want to do the work. A prologue with a good hook will make a reader more eager to start a chapter 1 than if there had been no prologue at all.
3. It sets up the structural framework for the entire book.
So this is a good piece of writing, ends with a great hook -- why not just make it chapter 1 rather than the prologue? Same thing, right? I would argue that this section works better as a prologue for the following reason: it sets up the framework for the story. The rest of the novel is concerned with the question set up in the the prologue: will the woman's curse bring the three accusers to justice? Structurally then, the prologue gives the reader a reference point for reading. Since Pillars of the Earth is an epic 400,000 word novel spanning several decades, presenting this question in the prologue provides the reader with some scaffolding around which to organize the reading experience.