The Kindle Create app is a handy tool for self-publishing authors, and I've spent more time than I'd like to admit fiddling with it. It supports a few key formats: DOCX, PDF, and HTML are the big ones. If you're working with a manuscript, DOCX is your best bet—it preserves formatting like headings and italics way better than a plain PDF dump. HTML is great if you're tech-savvy and want fine control over layout, but honestly, most folks stick to Word docs.
One thing that surprised me? It doesn’t natively support EPUB, which feels like a missed opportunity since so many e-readers thrive on that format. But hey, Amazon’s ecosystem plays by its own rules. If you’re converting from other tools like Scrivener, you’ll need to export to DOCX first. The app’s preview feature is a lifesaver for catching weird spacing issues before publishing, though.