My Christmas letter reached my nephew yesterday, having spent, it seems, six weeks orbiting the planet. So what went wrong? Nobody knows. We proofread the letter and the envelope. We added the right postage (albeit in a rather strange, printed stamp because the Post Office ran out of "forever international" stamps). We posted it only a few days later than we should have. But six weeks! And sometimes, no matter how carefully you (or your editor) edits, how well you (or your editor) proofreads, and how perfectly you (or your editor) make sure you've obeyed all the rules, some little errors slip by. The advantage of Print on Demand is you can fix them before too many people see them. If you have friends willing to point things out, and a sweet deal where new uploads of files (to your print or ebook service) are free, that's a really big advantage. If you have to pay for uploads, maybe less so. If you have to pay for changes, you'll probably want to balance perfec