Nothing else matters if they do not keep turning the pages. THAT is the first priority.
I think there's an analogy to that in standup. The first priority is getting the audience tuned in to you. They have to be engaged and they have to stay that way. If you don't have their attention, you're wasting time just moving ahead with material. If people aren't focused on what you're saying, nothing will be funny.
Ties in with what I see as the most common mistake new comics make: talking too much. I mean saying words that don't HAVE to be there. If what you're saying isn't leading to the funny part or the actual funny part, it's dragging everything down.