"Murder in the Zone"
or maybe "Death Thread", or even "The Killing Post"
Don't tell me! You're writing a murder mystery! Someone on a BBS decides to kill one of the other posters, due to some perceived slight, political disagreement, imagined disrespect etc.
The detective lurks for a while, then goes undercover as a newbie to try and trip up and track down the killer.
The entire book is written as a transcript of relevant threads, with the usual cast of idiots, the reader gets access to the same clues as the detective.
But the real killer is.......................................................
THE MILD-MANNERED MODERATOR!!!!
I love it.