Do You Use Reader's Guides?

It's just over a week until my cover reveal (those of you who signed up on the form to participate will get info soon! And if you still want to sign up, I'll put the form at the bottom of this post) on December 20th, and I've been thinking about my novel and trying to decide whether or not it's worth it to write a reader's guide for it. I myself always read them but from a writer's point of view -- what did that writer (or his or her editor or publicist or hired hack or whoever wrote the thin...