Lisa Lutz, a screenwriter, has written her first novel, The Spellman Files, about a fiercely funny family of private detectives.

Where did you get the idea for The Spellman Files?

I worked at a family-run PI firm in San Francisco in the mid '90s for about two years. There was this lovely office—extreme family-like atmosphere. There was nothing corporate about it. But every time the phone rang and you got off the phone, the bosses would harass you about who were you talking to, what did they say, all these rules. There were four phone lines, and you had to answer some of them differently, and some papers had to be shredded. It was a mix of warmth and total paranoia.

Did you ever get scared or carry a gun?

I was never scared, but we did have days when, for whatever reason, the doors had to remain locked because they were worried about certain people—the main boss actually carried a gun in his pants (retired FBI)! I didn't have a license to carry a gun. I was never allowed to drive on any surveillance.

Did you learn anything important from scripting Plan B [a Mafia spoof produced in 2000 starring Diane Keaton and Paul Sorvino]?

That I'm not a serious writer. This was really important. In high school I didn't know that I was meant to write comedic things. I was a "serious" writer.

Is The Spellman Files a spoof?

No. I see it as more grounded, a book about a family that happens to be detectives. We all have the tools of surveillance that the Spellmans have. And many families are utilizing them. We've become a society where we expect to just know what everybody's doing all the time. Most kids have cellphones and their parents know where they are at every moment of the day.

Is this mystery the first of a series?

I've agreed to two, but there will never be more than four. They aren't traditional mysteries. I want them to be "anti-mysteries." My heroine doesn't collect clues to solve a crime. The truth emerges in a roundabout way.

Paramount has optioned The Spellman Files. Will you write the script?

I don't want to write a screenplay ever again, whether it's my own or adapting. There are so many rules and so many limitations. It wasn't until I wrote my own novel that I realized I'm really liberated here. It's fantastic! I can't go back.