Why do Nancy Drew books have a cliffhanger at the end of every single chapter? Seriously. Every single chapter. I can understand having a cliffhanger or two near the beginning of the book, in order to make things exciting and grab the interest of potential readers. But why continue with cliffhangers throughout the entire book?
I mean, by the time the reader is on Chapter 8, cliffhangers stop working. A smart reader will recognize the fact that Nancy has been put in fake danger seven times already, and they won't be fooled again by another cliffhanger.
At some point, I think it's unnecessary to introduce a cliffhanger to make sure the audience keeps reading the book. For instance, if someone is on Chapter 11, odds are that they will finish the book. You don't need to cliffhanger them, to make sure they keep reading.
Here's what Anne Greenberg, the Nancy Drew editor of the 1980's and 90's has to say: "We've found that the stories are more interesting if they have at least three suspects. If the writer can provide a juicy red herring, so much the better. One element we knew we had to have was the cliffhanger. That tried-and-true device of literary manipulation grabs you by the throat and takes you to the edge and doesn't let go until you have no choice but to turn the page and get yanked into the next chapter with your flashlight batteries running low."
By the way, I'd recommend reading Chapter 7 of this book, if you're interested in seeing how they edited / wrote the Nancy Drew series, after Simon and Schuster bought the rights to Nancy Drew. That particular chapter is available for free.