The manifest names resources
Each manifest item has a unique ID, a path and a media type. The spine refers to those IDs to define reading order. A navigation table of contents is a different document, so reordering the spine does not automatically rewrite every contents link.
Replace a complete XHTML document
Copy a chapter from the source viewer, edit it, then supply its manifest ID and complete XHTML. Keep the html, head and body structure and preserve image links relative to that chapter. The source viewer never executes book scripts.
For a new order, list every existing spine ID exactly once. This prevents silent chapter loss. Open the result in your reader and check both sequential reading and table-of-contents navigation.
Use a two-chapter ordering example
Suppose the inventory shows intro followed by chapter1. To reverse the reading sequence, enter chapter1 intro in the order field. Both existing spine IDs must appear exactly once. Typing the XHTML filenames instead of those IDs will fail because the spine points to manifest identifiers. The tool refuses incomplete lists rather than silently dropping a chapter.
To fix a sentence, select the chapter in the source viewer and copy its complete XHTML into the replacement field. Enter that chapter’s manifest ID separately. Edit the paragraph while preserving its surrounding tags and relative resource links. A replacement containing only a fragment such as <p>New sentence</p> is not a complete chapter document and will be rejected.
Review links after structural changes
Moving an existing spine reference does not move its file, so relative image paths are normally unchanged. Rewriting chapter source can still break anchors, headings or stylesheet references. The structural check confirms that manifest resources exist; it does not validate every hyperlink target, every accessibility attribute or the relationship between a table of contents and your new reading order. Open several internal links in the final reader.