You're halfway through your novel, or maybe you're done with the last draft and something's just not quite right. There's something missing, you're not sure what it is. It could be the mid-point milestone. Go to Larry Brooks' storyfix.com for a detailed description of this crucial element in story structure.
Here's Larry's short definition of the mid-point milestone: new information that enters the story squarely in the middle of it, that changes the contextual experience and understanding of either the reader, the hero, or both.
Still not sure what this entails? Look at your own experience as an example, because these happen all the time in life, we just don't label them as such. Here's mine:
Once I worked at Costco. I was on the fast track for promotion in my department. I had been promoted fairly quickly, first to full-time (all Costco employees start out as part-timers), then to lead. (That fast, unexpected promotion to lead was my first plot point--it changed everything in my feeling about my job. I decided to move forward. It was no longer just a nice little part-time job for me. It would be my career.)
I had my eye on supervisor and/or manager of my department. My superiors seemed to like me. I felt like I was doing a good job. All was well in my world. The perfect opportunity opened up, and I figured I was a shoo-in. Then came the mid-point milestone. I can't remember exactly how it happened, but the curtain parted for me and I discovered that the warehouse manager disliked me intensely. I apparently had done something that upset him, and he was the grudge-holding kind who never forgot and always got his revenge. It was his warehouse after all, he was boss over all.
Once that realization hit, the stakes increased for me. And for him-- (the villain in my little story) I tried even harder to move forward, and he blocked me at every turn. But because I knew why, due to the "new understanding/mid-point milestone," it changed my understanding and experience of the situation. It was more emotionally-charged, other people got involved, it became a David and Goliath battle essentially between us.
(For some strange reason I cannot fix the italics on this post!!!!???? So sorry about the font-weirdness here.)
Anyway, moral of the story: Mid-point milestones happen to us constantly in life, and it must happen in our fiction. Without it, the structure is flawed and your story will collapse. Which is why I suggest it may be that "something missing" one might notice on a read-back of an otherwise really amazing piece of writing.
"Never give up. And most importantly, be true to yourself. Write from your heart, in your own voice, and about what you believe in." ~ Louise Brown
"Write something to suit yourself and many people will like it; write something to suit everybody and scarcely anyone will care for it." ~Jesse Stuart
"A writer's job is to take one thing and make it stand for twenty." ~ Virginia Woolf