As reader Roberto Suarez Soto asks:
You may start your book strong and confident, or doubtful and hesitating. But there's a point when you know that it's going to work ... or not. Maybe your initial strength diluted away, or maybe your initial doubts created a lot of conflict that ignited your plot. By that point your book should have momentum, should propel itself onwards; if it doesn't, you should hit "delete" and start anew.
When do people reach that point? After the first chapter? After the first paragraph? After the first word?