Sigil

Use Code View when a book’s structure or styling needs a precise correction, then inspect the preview before exporting. Sigil suits repairing a permitted personal ebook as well as preparing a publication. It is an editor, so readers who only want to open a book can use a simpler reading app.

The checkpoint feature compares snapshots of changes, and the contents generator uses multiple heading levels. Those tools help when a repair changes document structure rather than only a font or margin.