Amazon is phasing out their MOBI format. They asked their Kindle customers to move away from legacy MOBI creation workflows and advised to use EPUB. Furthermore, the fixed layout PDF format is a bad choice when it comes to a11y (accessibility). In fact, EPUB, and more specific EPUB 3.3, is the only futureproof format from the 3 mentioned ebook formats.

While I agree with my friend Huub below, there are reasons to still produce other formats. Always produce EPUB 3, but if it is fixed format, Amazon still requires a KF8 or mobi format for now. And many services (like Epic!) want a PDF along with the EPUB, so make that too: for fixed layout books, it is low- cost, and with all 3, you can go everywhere. Don’t forget to create accessible files! European laws will be requiring them.

If you want to format your manuscript and convert it to different ebook formats, here's what you should do: Use Microsoft word to do the initial formatting and design the interior of the manuscript. Next, go to draft2digital.com and use their platform to professionally format the manuscript and convert it to Epub or any PDF format of your choice. It's free. I hope this helps.

I always love that Smashwords provides an easy to follow guide to upload it and they will adapt it to the various formats selected. It can certainly be so overwhelming for authors to publish, your article helps break that down tremendously well!

This article is a good overview of the complexities of proper e-book formatting. Authors can choose to learn all this through trial and error (and error, and error) or write a check in five minutes to hire a pro. Experience in any field matters. Unless you have this knowledge and experience through years of training, there’s no substitute for working with someone who spends their days creating e-books, keeps up with the constant changes in tech, and delivers perfect files that always upload without issue. Creating a quality product is imperative if you’re serious about turning a profit. It’s worth saving up money and investing in your work to ensure your readers have a positive experience, as this will pay dividends in the long run.

As a self-publishing author, I validate and test my e-books by taking several steps. While it may be tempting to rush through this phase and release my work to the world, taking the time to validate and test can make a world of difference, I think. Firstly, it helps me identify any spelling, grammar, or formatting errors that may have slipped through the cracks during the writing and editing process. Secondly, by seeking feedback from beta readers, friends, or colleagues, I can gauge how engaging and coherent my writing is. Their input can pinpoint any confusing sections, plot holes, or areas where the narrative falls flat. Finally, I conduct market research continously to engage with my target audience and gain their insights.