I did this for three reasons:
1. To see how long the outline would "write out."I was aiming for about 30 chapters of 2400 words each, but my first chapter turned out to be 4500 words. Oops. Not surprising, since I tend to write long chapters. I thought it might be different this time, in First Person, with no other PoV characters, but I guess not.
So, unless I want this book to be 180,000 words (uhm, no), I'm cutting the number of chapters down. Twelve is a nice divisible number, with magical implications, and fits my theme of Knights for each month the Year.
2. To test Tone and Voice.The problem with outlining is that it doesn't tell you how the tone and Voice are working, and yet these are crucial for making the events in the book work. So even with an Outline First approach, I think it's critical to see, Hey, can I actually pull this off in the execution stage? Is this headed where I think it's headed?
My Chapter One turned out quite a bit darker than I had anticipated. My hero Brandon, it seems, is a runaway, who lives with a two junkie dropouts and a couple junkie ghosts in a haunted crack house, while he struggles to stay in high school, hold a full time job (swing shift) and avoid being hunted down and killed by his demonic Stepdad. I knew this from the outline but for some reason when I see how it plays out, I realize introducing heroin addiction in chapter one is going to add some Heavy into the book. On the other hand, I like the chapter. On the third hand, of course I like the chapter, I wrote it. that doesn't mean it's good for the book.
3. To See What the Story Promises Are
The key to good outlining, however, is to remain open to new ideas and new brainstorming. Instead of forcing my chapter to fit my outline, I want to ask what story this chapter (if I like it) is promising and then revisit the outline to see it will deliver. If I introduce addition as an issue, I have to deal with it later on in the book too. Am I willing to do that, or have I exhausted my interest with this one chapter? (Possibly.) If so, I can leave the chapter as "backstory" and start the book later. I can still refer to the hero's troubled "home" life (demonic stepdad, haunted crackhouse) but place less focus on it.
Now it's back to my Sticky Note Outline. I'm going to take out half the pages in my three-ring binder. I have to toss some stickies and add new ones. I think I might also switch from a Three Act to Four Act structure. Same thing, just one extra commercial break. ;)