novfmt

A lightweight Go CLI for EPUB maintenance: merge volumes, edit metadata and navigation, search/replace text.

Build

go build ./cmd/novfmt

Commands

• merge — combine multiple EPUB volumes into one omnibus file
• edit-meta — view or modify metadata and navigation
• rewrite — search/replace text (and optionally metadata)

Run novfmt -h or novfmt <command> -h for the full flag reference.

Note: edit-meta and rewrite modify the input file in place by default. Use -out to write to a new file instead.

Example workflows

Merging a multi-volume series

Download all volumes into a folder, making sure filenames contain volume numbers so they sort correctly (e.g. vol01.epub, vol02.epub, …). Then:

novfmt merge \
  -dir ./my-series \
  -title "My Favorite Saga" \
  -o saga.epub

Files in -dir are sorted numerically by the first number in each filename.

Fixing metadata and navigation after a merge

Dump the current metadata and nav to temporary files:

novfmt edit-meta \
  -dump-meta meta.json \
  -dump-nav nav.xhtml \
  saga.epub

Open meta.json in a text editor — fix the language, add a description, correct the title (useful for translated books where the title may be in the wrong language):

{
  "title": "Corrected Title",
  "language": "en",
  "description": "A short summary of the book.",
  "creators": ["Author Name"]
}

Edit nav.xhtml to fix the hierarchy — nest chapters under their volumes, group subchapters (2.1, 2.2, 2.3) under their parent chapter, etc.

Apply both changes and write to a new file:

novfmt edit-meta \
  -meta meta.json \
  -nav nav.xhtml \
  -out saga-fixed.epub \
  saga.epub

Search/replace text

Rename a character across the entire book:

novfmt rewrite \
  -find "Old Name" \
  -replace "New Name" \
  -out fixed.epub \
  book.epub

Preview changes without writing anything:

novfmt rewrite \
  -find "typo" \
  -replace "correction" \
  -dry-run \
  book.epub

Apply multiple rules from a JSON file:

novfmt rewrite -rules fixes.json book.epub

Future work

• FB2 conversion, asset cleanup
• Smarter nav merging that preserves per-chapter structure from each source
• Parallel extraction and asset deduplication