"I noticed that you would be about the same age as the lead character in 12 Hours of Halloween. To what extent is this novel autobiographical?"
The short answer is that 12 Hours of Halloween isn't autobiographical at all--well, not really.
12 Hours of Halloween is a supernatural tale set in 1980. The events of the story--which include encounters with various ghostly entities--are highly improbable, of course.
But you already knew that. What you really want to know is to what extent the lead character's basic circumstances mirror my own.
Like Jeff Schaeffer (and his two friends, Leah Carter and Bobby Nagel) I was born in 1968, So yes, I was twelve in 1980.
I also attended Catholic schools...and I grew up in Cincinnati. Just like the main character.
But that is about where the direct similarities end.
If you had known me at age 12, you wouldn't have mistaken me for the lead character.
Let's start with the basics: Jeff has a sister; I was an only child. My father is much younger than Jeff's father.
Nor did I know a girl named Leah...
I don't write about my own life for a reason. Generally speaking, direct autobiography makes for bad fiction.
I do sift the raw material of my experiences for fiction ideas, as was the case with Termination Man. (Termination Man is a corporate novel set in the automotive industry, where I worked for a number of years.)
However, I wouldn't think of publishing novelizations of periods in my own life. Those novels wouldn't be very exciting to read--even for me.
So although 12 Hours of Halloween--as well as Termination Man--draw heavily on my "real life" experiences, neither book is "real life", or at least my real life.