Just started prepping for my first game of EC, and I wanted to give some feedback to Paizo on the NPC subject.
The whole point of buying an AP is that it makes things easier for a GM, right? So what do you think happens when you give the players a murder mystery, and ask them to investigate it? That's right, they look for clues and suspects. Naturally they are going to start asking about all the colorful characters everywhere. Circuses are full of crazy people, everyone knows that. Sure the AP gave some good reasons why the snake lady isn't a suspect... but what about everybody else? OK, nobody can control rats; how do they know that? Aren't there some animal trainers here? Do druids not exist in circuses? Oops, one of my PCs is one, so there goes that theory.
Also, there are TWO crucial skills checks during the short investigation to gain clues. (Already decided those will be freebies.) A medicine check to know it was a snake, and another check to find the rat tracks. If they fail one or both of these, they have no reason to jump to the conclusion that it "must be someone that can control snakes and rats". Or maybe they just don't connect the dots. Either way, they're almost guaranteed to ask about the NPCs, And I have nothing but a couple pictures of some tricks to draw from. So that leaves me with two choices- spend a ton of time fleshing out characters just to show the PCs they're all saints, or railroad the hell out of them. I don't like doing either of those.
I understand that you can't fit everything into a book. You need to keep costs down, etc. I get it. But give me something. A sentence like "Mordaine: Irriatable. Diva, wants to be the main star" is enough for me to build from. All of that could fit into the space one, maybe two monster stat blocks take up. Do you really need a giant flea? Just use something from the Bestiary.
Sorry that this comes across as ranty, but I'm disappointed in the amount of prep work I need to do after buying this AP.
In short- don't give my players a murder mystery, and then not provide the GM with any info to give them.