You've just published your 18th Amos Walker novel, Nicotine Kiss. How did you come to create your detective hero?

I had an odd upbringing; I grew up in the country, and the people I most related to were my parents and their generation, who had gone through Prohibition, the Depression and World War II. So when I discovered the classic private-eye genre, set during that time-period, it just seemed to be the thing for me. Reading Raymond Chandler, who was very aware that he had created an anachronistic character—a knight-errant, lost in the world of Prohibition and the Depression—it struck me that it would be interesting to create a similar figure, a classic private eye adrift in the world of Vietnam and Watergate.

How has Walker changed in the almost three decades you've been writing about him?

He has aged; he's a little sadder, a little mellower than he was in the beginning. While he still makes wisecracks, they're more of a self-defense mechanism now. He doesn't have the cocky attitude that we first saw in Motor City Blue, because he's been knocked down too many times. He knows now that it's not enough to be a good man, and that he can't fix the world. All he can do is clean up his own little dirty corner of it—and that's not going to last for very long. He's resigned himself to that, but what makes him a hero is that he never totally gives up.

What challenges have you faced in writing about Walker in a post-9/11 world?

You just can't write a pre-9/11 novel unless you very clearly set it in period. The world has changed and there are issues that need to be addressed. I'm writing a snapshot in time, but want the books to still have meaning if they're read in 30 years. I can't have Walker do a lot of things that he could do very freely before 9/11—for example, I can't have him meet a plane at the gate anymore. There are realities we now have to deal with, but I try not to make it a central focus, which would feel artificial.

How does Walker differ from Spenser?

I'm a big admirer of Robert Parker, but I have the sense he's grown bored of Spenser, and it shows in his recent books. Unlike Walker, Spenser wisecracks too much, and for all the wrong reasons; wisecracks aren't just to entertain the reader—they do, of course, but if you worked with police officers, as I did, as a journalist, you realize why they have that sense of humor—it's a way of distancing themselves. Once the wisecrack becomes a knee-jerk reaction just to make people laugh, as it has with Spenser, it begins to lose all significance.