I've enjoyed Rhys' and Jane's comments on blood, gore, and the appearance of a dead body in mystery fiction. My position on blood, gore, and the heretofore unmentioned delicate subject of sex is the same as John Grisham's. He says that he never writes anything his mama can't read. Me, neither. And I don't write anything my kids can't read. (Unless it's too hard for their age at that time. If they're old enough to be able to read the words and understand the plot, then they're old enough for my work.)
As for the appearance of a dead body, I believe that a perfectly satisfying mystery could be written without a single murder, but I'm not convinced that it could be published as a mystery in today's marketplace. Readers have expectations, and publishers like to meet those expectations. To be more precise, publishers like to meet the expectations that they think readers have. So even if a non-murder mystery were written that was so wonderful that everybody on the planet would buy it and read it, it would never reach bookstore shelves unless a publisher could be convinced of its marketability. It's my personal opinion that the only writers who could get such a book published are people who have so many bestsellers under their belt that their next book is almost guaranteed to reach that milestone.
This is related to the question of when the first body must appear. In today's marketplace, almost every first novel will feature a corpse within the first 50 pages and probably within the first 10. Why? Because no agent or editor will spend much time reading the entire manuscript of an unknown quantity. They'll ask for 10 or 20 or 50 pages. If nothing exciting happens in that excerpt of the book, then they won't be asking to read the rest of it.
In subsequent books, a writer who has earned his/her editor's trust will probably be given more leeway in this area. As I said above, a multi-bestselling author can get away with just about anything.
I was discussing this issue with Jim Huang of The Mystery Company in Carmel, and I told him I thought it would make a good panel discussion at Magna Cum Murder, where he organizes author panels. He responded by asking me to give a one-hour talk. By myself. Eek.
Being an engineer, I'm fairly well convinced that there is no problem that can't be tackled through the use of a spreadsheet. So I went to my bookshelves and took a highly scientific sample (i.e., an armload of books I'd read recently.) I configured my spreadsheet to accept book title, author, pub date, and the book's chronological position in the author's output, then sorted the data several ways.
The results? Bodies do in fact drop early and often in first novels. Later novels, even second novels, show much more variation. It also appears that editors were more forgiving of late bodies in the past than they are these days, so this is a relatively recent trend.
Marketing realities determine what gets published. This is a business, after all. But if you like stories that are a little different from the usual, it makes sense to buy more of those. Voting with one's dollars is one of the most effective weapons of change in a capitalist society. Let's think about that one for a minute. What would happen if, just for a day or a week or a month, women refused to buy shoes that hurt their feet? We could bring Madison Avenue to its knees!
Okay. Revolutionary rant over. Back to mysteries...