Write Wild Workshopping
Whether you're a writer of mysteries or not, it's always a good thing to present your reader with a challenge. The kind of mentally stimulating challenge that draws your reader in and has them emotionally interacting with your plot, characters and subtext.
As a writer you already know that writing isn't a passive activity. Far from it. Reading isn't passive either, or at least it shouldn't be. If you're reading a book and your mind keeps wandering elsewhere, all that's happening is that your eyes are following the text but you're not absorbed by the story.
A writer writes mainly to engage a reader and one of the best ways of drawing your reader in to your story is through mystery and intrigue. If you're thinking Sherlock Holmes, Poirot or Morse, think again. I'm not talking about plot here. What I am talking about is evidence.
If you have a draft of your manuscript, search for any/all evidence that demonstrates the role your reader will play in bringing your story alive. In other words, where and why is your reader most likely to be caught up by your story. What little nuggets are already in your writing that will cause your reader to become wholly absorbed?