Sometimes, readers like prologues, but they don't like how long they are. Some say that they're too short.
So the question here is...to prologue, or not to prologue?
I like to write prologues, it makes me understand my characters better, and to see how far they have come since then. But I don't like reading them, not really. Especially those really long ones in classics. I don't want to read it, since it's usually boring, and I just want to get to the story.
BUT, the one thing that's important when writing a prologue is not to put important information that a reader would miss if they didn't read it. A prologue is just to inform the reader of how the characters got there. Not to throw a much of information that they'll miss if they just skip right over it. They're just there for the readers that want to know more.
So if you're trying to figure out if you want to write a prologue to your book, just think of these steps:
1. How long should you make it? Long, short? In between?
2. What should I have in it? Is this really necessary? Do I need one?
3. Make sure not to put important facts in there, it's just there for those who want it.
There are some easy steps on why or how you should write a prologue. If you want an example, you can read the prologue of THE STORM here. :)