The format of your eBook will be depend on its content. There are two types of ePub:
eBooks are digital objects built to be read on different devices, with different sizes and uses. This is why most eBook files are set to be "reflowable", so that the text adapts to the screen's size and settings.
All books composed mainly of text, in general, are created with this approach. They must be distributed in the reflowable ePub format, otherwise they will be blocked on many stores.
tip: ePub and mobi (for kindle) are equivalent formats created by different companies.
ePub (Fixed Layout)
However, some books may need the text and images to keep to a specific layout, regardless of the screen size. That is the job of the Fixed Layout format - ePub 3.
With this format, the various elements (images, text, quotes, etc..) have a fixed position within each page. They remain in the same position no matter which device is used.
tip: ePub FXL, KF8 are equivalent formats created by different companies
This format is particularly suitable for children's books, technical manuals, picture books, guide books, comics.
Whichever of the two formats you need, you can create and prepare your eBook using StreetLib Write, our totally free, online tool. Check out our other Help Center articles for more information about the tool and formats.
If you want to a a professional to take care of preparing your book, you can hire conversion services via StreetLib Market.