There are two kinds of EPUB and they are not variations on a theme. Choosing the wrong one produces a book that is unreadable in a specific and embarrassing way, so it is worth ten minutes to get right.
Reflowable
The text adapts to the reader. They choose the typeface, the size, the line spacing and the margins on their own device, and the words re-wrap to fit whatever they picked.
This is what almost every ebook is. A novel, a memoir, a business book — any book that is essentially a stream of paragraphs — should be reflowable, and nearly all of the Kindle store is.
The consequence people find hardest: there are no pages. Not fixed ones. Page 47 depends on someone's font settings, which is why a Kindle shows "location" or a percentage instead. Anything that depends on a page existing — a typed contents page with page numbers, a cross-reference to "the diagram on page 12", running heads — is meaningless and should be removed rather than carried across.
Fixed layout
The page is a designed unit. Text and images sit exactly where you put them, and the whole page scales up or down as one thing, like a PDF.
This is right when the arrangement is the content:
- Children's picture books, where the words sit in the sky above the whale
- Cookbooks with photographs and a specific relationship between them
- Comics and graphic novels
- Highly designed non-fiction — art books, some textbooks
The cost is real. A reader cannot enlarge the text, because enlarging it would break the layout — they zoom the whole page instead, which on a phone means panning around. Accessibility is significantly worse. Files are much larger. And it is more work to produce, because every page is laid out individually rather than flowing.
How to tell which you need
One question: if the reader doubled the text size, would the book still make sense?
For a novel, yes — bigger words, more screens, nothing lost. Reflowable.
For a picture book where a line of text is positioned against an illustration, no. The words would slide away from the thing they refer to. Fixed layout.
Most books answer this immediately. If yours is genuinely ambiguous, it is probably a mostly-text book with a few images, and those work perfectly well reflowable with the images flowing between paragraphs.
Poetry is the interesting case
Poetry is reflowable — but it is the reflowable case that breaks most often, and for a reason worth understanding.
A poem's line breaks are decisions. In a reflowable book, a line longer than the screen has to break somewhere whether you like it or not, and most tools let it wrap flush against the left margin, where it is indistinguishable from a new line of verse. The poem changes shape and nothing tells you.
The fix is not fixed layout, which would make the poem unreadable at large text sizes. It is a hanging indent, so a wrapped line sits visibly under its own line rather than beside the ones around it. That is what our poetry formatter does, along with preserving indentation as non-breaking characters that survive conversion.
What we make, and what we don't
Everything our tools produce is reflowable. That is deliberate: it is the right answer for novels, non-fiction, memoir and poetry, which is what the tools are for.
We do not produce fixed-layout EPUB. It is a different document model rather than a setting, and rather than emit something that half works we would rather say so. If you are formatting a picture book or a photographic cookbook, this is not the right tool — and a page telling you otherwise would waste your time and then break your book.
If you need reflowable
Our EPUB formatter produces a validated, reflowable EPUB 3 from a Word file, and the KDP and Kindle formatter does the Amazon-shaped version of the same thing. Both check the result with EPUBCheck before you download it — see what EPUBCheck errors mean if you have a file that is failing somewhere else.