About the best that I can say is that if you are publishing your first novel and your initial edit letter isn't 15-20 pages, ask for another editor.
Yeah, I know it seems like a lot, but often things that are inside your head never make it to the paper. While it might make perfect sense to you and to anyone you have involved in the writing process, often there are defects in the plot or the characters' motivations that will be caught by a skilled editor. If you're lucky, you'll also get one with a sense of humor! Here are a few real-life examples from our first edit letter with a NY publisher:
"Here is how I see Tony in most of the book: a very suave but ordinary-looking James Bond type. A trained assassin-for-hire. Secretive. Pleasant but dangerous. Mostly honest, but willing to bend the rules for a good reason, but it has to be *his* reason. He likes to have a plan and a back-up plan. He's a good judge of character and only gives information that is pertinent to who he's speaking to.
The other side of Tony you've presented is like Joe Pesci in
My Cousin Vinny. Tough and introverted, but NOT a controlled, silent, snarky James Bond type. Which one is he? You guys have to choose. He can't be one sometimes, and another at other times. It's very out of character and pulls the reader out of the book."
Now, of course, this meant that we had to make MAJOR changes to character is certain points of the book because, ultimately, she was right. He had two different personalities.
"Does the man NEVER brush his teeth? I mean -- eeww!"
Of course, it never occurred to us, but she was right. Most of his day-to-day routines were off-stage.
"Right now, in one day:
Tony wakes up
Sue comes back
they decide to date
they eat breakfast
they go to Tony's house
they go to the bank
they go shopping
they fly to Vegas
they go to a bunch of casinos
they go to Leo's casino
they play there for a couple of hours
they have all of the altercations, Sue is kidnapped, etc.
they "escape" and confess their almost-love
it takes 14 hours to drive back to Tony's house
That's a DAMN full day! And they haven't eaten since breakfast!"
Haha! Again, it never occurred to us. Of course, the READER would spot it right away. This is why an editor is so important, because you're looking at it from the eyes of someone who has lived the lives of the characters for months or years! It takes fresh eyes to see the gaping plot holes.
Does that help any?