Being a writer is pretty brutal. Even the good reviews might contain comments that feel like arrows piercing your innards. That's why, as the author, you've got to be the toughest person in the room when it comes to your own story. Before you present it, you've got to cut it into usable slices your audience can digest. Just how adept are you at carving up your story?
Knife Skills
I'm referring to editing techniques, of course, but I'm doing it in a colorful way (I hope). You have to be a real killer when it comes to your own story lines and plot. Too many sub-plots muck up a story, and over-long descriptions get skipped.
Length is a factor in each and every single book, and it's a problem that only goes one of two ways: the book is too short, or too long. Rarely is the length ever "just right," because if a story is really good then readers want more of it. But books can be too long as well. In fact, this is a very common characteristic among new authors who have written only one or just a few books.