Truss, best known for her book on punctuation, Eats, Shoots and Leaves, makes her mystery debut with A Shot in the Dark (Bloomsbury, Nov.).

What appealed to you about combining humor with a mystery plot?

I seem to have read quite a lot of funny crime fiction in my life, so I’m pretty sure I haven’t invented a new genre or anything, but I suppose I’m exposed, as we all are, to so much serious crime detection on television that writing like this is sort of my answer to it. Also, I do seem to like making things hard for myself. The denouement in a comic crime novel has to be not only satisfying and a decent surprise but also, if possible, funny.

You’ve written that “what really interests me in life is how other people think, which is why the dramatic monologue is probably my favourite form.” Why?

I do love writing monologues, and I think they’re a good training for working with characters in any form—play, story, or novel. It’s often an exercise I set for would-be writers, and it’s interesting to see how hard they find it. In a monologue, you not only have to inhabit another person’s psyche but cunningly expose the limits of that person’s self-knowledge. I think you probably can’t write comedy if you’re not interested in the things people don’t know about themselves.

Is there a way in which your work to educate readers on punctuation connects with your mystery writing?

I’m sure it must. Maybe both are my way of saying: pay attention to the detail! To be honest, though, I never thought of Eats, Shoots and Leaves as educational when I was writing it. I assumed it would be read by people who already knew as much as I did, but had just never thought about punctuation as a subject. I have been hugely gratified that people have subsequently found it so helpful.

Why do you think that Eats, Shoots and Leaves became so popular?

All success is about timing, so I expect it was that. When the book came out, the general response I heard was not “How interesting” or even “How niche” but “At last!”—as if people had been waiting for a funny book on punctuation for years and years. For me, it was like being in the middle of a feeding frenzy. Nobody knew this desperate and chronically deprived specialist market was out there, of course. I think it came as a surprise to the whole book industry.