Define Success

Aside from personal satisfaction, I wonder now what would be considered the threshold for success for a self-pubbed book (electronic and/or paperback). Before the onslaught of electronic and paperback self-pub options that exploded on the scene 4-6 years ago, I read that 500 sales was considered a best-seller for vanity press -- with most of those successes being cookbooks not novels. After only a two months with a published book and watching the rise and fall of rankings on various sites, I can believe 500 would be considered a best seller. 500 sales, I'm hoping so with ONE PROMISE TOO MANY and more.