Richard Ridley wrote a post for CreateSpace with advice on writing book descriptions, what you might think of as the book blurb or flap copy. Reading it, I thought his advice was pretty good. You won’t get the gist without his explanation of each of these points, but here’s the bare list:
1. Don’t include subplots.
2. Keep it under 150 words.
3. Write in third person, present tense.
4. Use emotional power words.
5. You are not the author.
He’s talking generally, but for crime novel blurbs, I’m going to propose 2 additional items that might, at first, seem counter-intuitive:
6) Don’t waste precious words explaining your protagonist is at risk. Why? Because 99% of the time, the protagonist is under threat, and, therefore, there’s nothing unique enough about that to grab attention. I mean, not from a nutty reader like me who reads tons of book blurbs. If something about the protagonist’s peril is unusual or consumes such a huge portion of the novel that the existential threat is the main plotline, tell me. Otherwise, don’t bother, unless you’re going to find some phrasing that isn’t generic or played out. I pulled these examples at random:
“…the unthinkable is about to happen…the end may be something worse–far worse…”
“…the nightmare is not over…and it may be closer to home than she ever imagined…”
“…Can she find the truth in time to save her own life?”
The situations might be (and I hope will be) terrifically suspenseful when being read, but as-is, they’re awfully common. And that means none of these words can help me differentiate between your book and another, the task which is every new release’s biggest challenge.
6a) Don’t dwell on the fact there’s a murder *gasp* or even several involved. Because there always is–that’s why I’m reading a crime novel after all. There’s nothing wrong with either of these story elements, of course, because…um, crime novel. And if you spent NO time on them during the novel itself, I’d feel righteously shortchanged. But too much space in the blurb when the info isn’t specific or unusual (“the body count rises again…” vs. “more mutilated birdwatchers”), and you’ve wasted words that could’ve communicated things I can’t already assume.
I find myself intrinsically interested in book descriptions that soft-sell the hero’s risk and murderous elements of the story, letting the setting, character, even implications of voice and language carry me toward one story over another. Looking for the examples of blurb-wastage I listed above, I discovered how many of the better books I’ve read recently have descriptions that don’t feature the ploys in 6 and 6a, so for me, that might be reason enough to avoid them. Writing a good blurb is acknowledged to be agony, like having to break your bones and amputate toes to cram a full-sized foot into a plastic doll’s shoe. But as a person forced to read a lot of them, I’m imploring you to consider whether you really need to risk anyone’s life writing yours.