My prologue is currently sitting at 36 pages - or 9000 words. I'm about to have my friend review it. She is an avid reader and is mercilessly honest. The prologue is actually like a mini-story which sets up the environment for the rest of the novel. It uses unique characters. Obviously, I have some room to cut down if I need to, but are there any rules of thumb for a prologue? It's certainly not an info-dump, and it leaves more mystery and questions rather than answers.