Choosing a KDP format requires two separate decisions: whether the book is set to horizontal writing and whether its content actually reflows at different viewport widths. In this two-chapter sample, the local export preserved ten paragraph markers and one image without declaring a fixed layout. The planned three-viewport rendering test was not performed, so the article-specific Stage 4 result remains partial.
Give horizontal setup and reflow behavior separate verdicts
Horizontal writing defines reading direction. Reflow defines how lines and pages are recomposed when the viewport or font size changes. They answer different questions.
| Verdict | Evidence to inspect | Result in this run |
|---|---|---|
| Horizontal writing | Export setting and reading direction | Confirmed in the local output |
| Reflowable structure | Absence of pre-paginated, preserved paragraphs and image |
Confirmed |
| Reflowable rendering | Line flow and image position at narrow, medium, and wide widths | Not tested |
The EPUB 3.3 specification makes reflowable layout the default when pre-paginated layout is not declared. That package fact does not establish that a particular manuscript remains readable at three viewport widths.
Use two chapters, ten paragraphs, and one image
The article-specific sample contained two horizontal chapters, ten paragraph markers, and one inline image. Recording those starting values makes the comparison objective: two chapters must remain in order, all ten paragraph markers must survive conversion, and the one image must remain packaged.
The visual plan used three viewport classes—narrow, medium, and wide. At each width, the intended checks were reading order, horizontal overflow, and whether the image stayed near the relevant text. Because image and screenshot work is outside this revision, none of those three viewport observations is represented as completed.
Choose the format through two general testing stages
The first stage is structural. Work on a copy, record chapter, paragraph, and image counts, generate the EPUB, and inspect the package document and body XHTML. Confirm the reading order, the layout metadata, and every expected resource. If a count is wrong, return to the input or conversion before opening a viewer.
The second stage is visual. Review Amazon KDP’s supported manuscript formats, open the same file in Kindle Previewer, and vary the viewport and font size. Record paragraph flow, overflow, and image placement at all three widths. Only then can the reflowable format be selected for this manuscript on visual evidence. A book that must preserve page coordinates requires a different fixed-layout assessment.
Nine commands confirmed structure, not rendering
In a dedicated Rune Studio workspace, I set the series to Japanese horizontal writing, set the volume information, selected the two chapters, fixed their order and TOC inclusion, reviewed the export plan, exported the EPUB, and ran the local inspection. The evidence records a command_count of 9.
The observed values were valid=true, a spine count of 5, one packaged image, and zero missing images. The EPUB navigation document and NCX were present with two items each, targeting p001.xhtml and p002.xhtml in order. The two chapter inputs and all ten paragraph markers were found in the output XHTML, and no pre-paginated declaration was present.
Those observations confirm horizontal setup and a structurally reflowable package. They do not include the planned three-viewport rendering check. The correct Stage 4 status is therefore partial, not passed.
Return to the verdict that failed
KDP acceptance, rendering at the three widths, device operation, and appearance across all reading systems remain unverified. Use the failed check to select the recovery point:
- If the output is not horizontal, return to the series writing-direction setting.
- If the two chapters are reversed, return to source selection and chapter order.
- If fewer than ten paragraph markers remain, return to the source text or XHTML conversion.
- If the image is missing, return to its source reference and package inclusion.
- If one viewport shows overflow or a detached image, revise the relevant CSS or image dimensions and repeat all three viewport checks.
A single successful width is not enough to complete this format decision.
Rune Studio provides the export workflow, not the missing viewport evidence
The current macOS version of Rune Studio documents an EPUB 3 export wizard for writing direction, language, volume data, source files, chapter order, TOC inclusion, and metadata. The output includes the package document, EPUB navigation document, NCX, and body XHTML. These are Stage 3 capabilities described on the Rune Studio product page and in the product documentation.
The two chapters, ten paragraph markers, and one image are Stage 4 observations from this sample. The unperformed three-viewport test belongs to neither category and must remain an open limit.
Conclusion: keep the format decision partial until three widths pass
Horizontal and reflowable refer to direction and layout behavior, respectively. This sample was exported horizontally, preserved two chapters, ten paragraphs, and one image, and contained no fixed-layout declaration. Its structure is confirmed. Because rendering at narrow, medium, and wide widths was not tested, the overall article-specific result remains partial. Test the same EPUB at all three widths before finalizing the KDP format choice.
