There are a lot of different ways to approach writing a book. Some people follow Lewis Carroll's advice - Begin and the beginning, and when you get to the end, stop. Others write a scenes out of order and then cobble them together when they get done. Whatever works for the writer is fine by me. You know, as long as the end result is well-written.
Personally, I write the Lewis Carroll way. Linear writing. I start writing at the beginning and work my way forward scene by scene. Going out of order screws my brain up. For the most part.
You see, sometimes I'll be writing along in a nice straight line - or rather a horribly crooked line that still goes from A to B to C to D, etc. - and then I'll realize I had scenes I should've written BEFORE the scene I just finished. Backtrack! When that happens, I just need to remember how to find my way back. Tie a string, so to speak, so I can follow it back when I'm done.
This happened to me last week. I finished a scene with the hero and then wrote a scene with the villain. THEN I realized that I had a whole day's worth of stuff for the hero to do before the villain scene that night. Oops.
Then, a day later, my brain went and gave me a perfect set of scenes for closer to the middle of the book. Derp. I wrote the bones of those down in a notebook and tried to get back to my string.
This, of course, is just first drafty stuff. In edits, I can and do get away from the linear thing if I need to. Especially if the editor goes 'you know, this scene should really go AFTER that scene, not before it' and when she points out 'you never did show what happened BEFORE this to make this happen.' And then I go 'DERP' and realize I skipped over that to get to this.
But the first draft? I like it in a line. That's how readers are going to read it, after all. Although, I have read books that aren't linear either. They kind of confuse me. Unless it's a drop of backstory here or there. To me, that's still in a line because it's what the character is thinking about right then. I read a Spillane novella the other day that started at the end and then came back to the beginning and then later - at the right point - went back to the end again. It worked out okay, but it confused me.
Maybe it's just me. What do you think?