But what is judging a major literary prize actually like, and how does reading so many books affect you? Ms. McDermid talked through the life of a Booker Prize judge in two recent interviews, although she gave no hints about her favorite for the prize (“I have a top three. That’s all I can say,” she said). These are edited excerpts.

Were you surprised to be asked?

Well, yes. I’m not someone who instantly springs to mind as a judge of literary fiction. I write genre novels. I occasionally appear on slightly ridiculous comedy news programs on the radio. I don’t write 10,000-word essays for The London Review of Books. But it’s great that the Booker looks for a range of judges. It’s not narrow and self selecting.

How many books do you normally read a year?

Maybe 100.

So did you think twice about reading 171 in seven months?

I thought it’d be tough. I thought it’d be hard work. But I also thought I’d be able to do it. I mean, I read quickly. But it was a huge ask. It did just swallow up my year. I got to a point where I was actually dreaming mash-ups of the books I was reading. I would wake up in the morning and go, “Did that happen?”

Did you read all of them?

I would say we “assess” all the books. To be honest, there’s some when you’re not very far into it and you think, “This is not going to win the Booker Prize.”