Your opening pages are the first impression the reader has of your story. Don’t throw them away.
When I’m reading, I want to imprint onto a character and follow them about, seeing the world through their eyes. I’ve learned to tolerate two points of view, since that’s endemic in Romance novels these days, but any more than that and I become less invested in the characters. I start to lose interest.
One common mistake that I see new writers make is starting out a story with a prologue. Almost invariably, the prologue is in the point of view of a character that I’m not going to meet again for several chapters, maybe not until the end of the book. This is throwing away your prime time slot on a character who does not play an active role in the story.
As I read the story, I’m still waiting in the back of my mind for this original character to come back. They’re the one I first met in this world. I imprinted on them. Starting off with someone who then disappears is a great way of ensuring that I’m never going to be fully involved in the main POV characters. It weakens the link I have to the story and makes it much easier for me to put the book down.
I’ve heard authors argue that this POV character is going to make sense once the reader makes it to the end of the story. That assumes that the reader is going to care enough to make it to the end. Why should they care? You’re telling them you have a big secret and they have to finish the book to find out what it is. As a reader, my response is “So what? I don’t see any point in learning this secret. It feels like you’re playing a game with me. If you don’t give me a reason to care, I’m going to feel manipulated.”
The whole reason I start to read a book is that I’m looking for a reason to care. You need to hook my interest within the first few pages or I’m going to put your book down and go find something else to do. Don’t waste your first pages on a prologue or on a character who isn’t going to show up again until the end of the story. If the information is so important to the story, slip it into the active story line bit by bit. If the character is so important to the story, make them the main POV character of the story.