A couple of years ago, California writer Mary Roach was walking down the street when she suddenly heard her friend calling her name. "Hey, Mary?"

It would have been a mundane occurrence if her friend hadn't been dead. Was it her mind playing tricks on her, or was it really a voice from the other side? Mrs. Roach wondered if there was any scientific evidence of life after death. The result of her curiosity was Spook: Science Tackles the Afterlife, released by W.W. Norton in October 2005. Spook is a very funny book with a wide territory. It moves from the historic attempts to weigh the soul, to modern day India where reincarnation is considered a fact of life, to medium school, which she flunked.

"I have always found paranormal research to be surreal and entertaining," said Mrs. Roach. "When I was a kid I played with ouija boards and went to graveyards. It is entertaining. It is also interesting that there is possibly a mysterious world that we can't access until death."

"I am not a sceptic with a capital S," said Mrs. Roach. "I am just applying critical thought to the question. I find the sceptic groups to be overly dismissive. They have made up their minds before they begin."

Spook didn't turn into a book that would really please true-believers. Mrs. Roach said if there was really strong and compelling scientific evidence of life after death, you would have heard about it by now.

"The book is really about the pursuit as much as what the pursuit has turned up," she said. "I was fascinated by the creativity that people have applied to answering the question. Someone has described Spook as 'This American Afterlife'."

One of the more amusing chapters in Spook chronicles Mrs. Roach's brief foray into a medium school in England ? a place where people go to learn how to channel spirits. "Flunking medium school didn't hurt as much as it would have had it been welding school, or something I would have pursued," she said. "I am okay with it. I knew I didn't have any natural aptitude. It wasn't a community of people I would fit in with."

Mrs. Roach said, if there is really life after death, from everything she has read, it is pretty boring.

"I don't think I can take a whole eternity of being dead," she said. "In the book I quote Rev. G. Owen's description of an afterlife. He said there wouldn't be a need for doctors, but there would be interesting things for them to study.

"Speed boats would fly through the air. Those kind of things I could get behind, but just floating around sounds boring, and being a peeping tom on your relatives and friends sounds equally disturbing. I might prefer to simply not exist." She said so far the reaction to her book has been mainly positive.

"When people email you, they are usually people who like what you are doing," she said. "People who don't like the book usually put it down. I get lots of nice emails from people. The reviews were good. I sent The Paranormal Society a copy. The editor of their newsletter said there would probably be a lot of 'squawking and flapping of feathers' from society members. I would imagine that I do have a nasty review in there, but my subscription ran out long ago. I don't subscribe to the types of places that may have been viscous."

If a book about the afterlife sounds strange, her first book, 'Stiff: The Curious Lives of Human Cadavars' was equally odd.

"There is no obsession with death," she said with a laugh. "Stiff grew out of a column I wrote for Salon magazine. I found the topic fascinating, and it was something no one had written about. I thought people would find it interesting and it would sell books. Spook was an obvious follow-up."

And Spook has indeed sold books. It was on the New York Times extended best-seller list for almost a month.

Mrs. Roach has been freelance writing full-time since 1984. She has written for magazines like Salon, been a freelance copy editor and even done some public relations writing for the local zoo, working in a trailer next to a gorilla.

Her next book is due out in the Fall of 2007. She is staying tight-lipped about what the topic will be.