Amazon says (not me) that for best results, you should upload in DOC/DOCX (.doc/.docx) or HTML (.html) formats.
Option 1: Amazon has a free step-by-step guide on how to do it yourself.
If you decide to go down this route you need to be aware that it can be quite tricky, and if you don’t get it absolutely correct there are likely to be errors in the Kindle version of your book. Anyone buying your Kindle book will have seven days during which they can return it for a full refund. The most commonly cited reason for returning books is poor formatting. So it needs to be spot on.
Having said that, once you’ve uploaded your file to Kindle, you have the opportunity to view it as it will appear on various mobile devices, including a Kindle and an ipad. In order to do this you have to download a piece of software from Amazon. The download you need is right there on the page when you get to this bit so it’s easy. I would highly recommend doing this, as it costs nothing, apart from your time, and it means that you can be sure that what you are putting out there is correct, and how you want it.
Option 2: What I did: buy Scrivener software from Literature and Latte
This is what I did. It costs $40 (about £25) at the time of writing, and you upload your manuscript to Scriviner so that you can output it as a Mobi file (see list above). Scriviner is an award winning writing tool and is used by writers to produce novels, non-fiction, scripts for plays and more. It makes formatting and editing your manuscript easier and will compile your novel, for example, for Kindle as well as other medium. Originally it was designed for Mac users but there are versions for Windows as well as Mac users now.
Literature and Latte have support forums which can help you when you get stuck.
Option 3: You can also pay someone who offers a conversion service.
I’m afraid I can’t recommend anyone at this stage as I haven’t used such a service but I will let you know if I find someone.
That gives you a flavour for the different routes and I will explore this topic more in the weeks to come as I produce my own Kindle edition of Forever Lucky, my next novel.