Sigil Portable is an ePub ebook editor with support for both WYSIWYG word processor style and direct code editing. It's packaged in PortableApps.com Format so it can easily integrate with the PortableApps.com Platform. And it's open source and completely free.

Sigil is a multi-platform EPUB ebook editor with the following features.
Sigil provides advanced automatic conversion features for all imported documents to the Unicode text encoding.
Sigil also offers a metadata editor with extended support for all types of metadata entries (over 200) that enable you to insert a full description for each.

Features
* Online Sigil User's Guide, and Wiki documentation
* Full UTF-16 support
* Full EPUB 2 spec support
* Multiple Views: Book View, Code View and Preview View
* WYSIWYG editing in Book View
* Complete control over directly editing EPUB syntax in Code View
* Table of Contents generator with multi-level heading support
* Metadata editor with full support for all possible metadata entries (more than 200) with full descriptions for each
* User interface translated into many languages
* Spell checking with default and user configurable dictionaries
* Full Regular Expression (PCRE) support for Find & Replace
* Supports import of EPUB and HTML files, images, and style sheets,
* Documents can be validated for EPUB compliance with the integrated FlightCrew EPUB validator
* Embedded HTML Tidy: all imported files have their formatting corrected, and your editing can be optionally cleaned

Sigil Portable is packaged in a PortableApps.com Installer so it will automatically detect an existing PortableApps.com installation when your drive is plugged in. It supports upgrades by installing right over an existing copy, preserving all settings. And it's in PortableApps.com Format, so it automatically works with the PortableApps.com Platform including the Menu and Backup Utility.

Sigil 0.7.1 2013.03.03
- Implement issue 2058: Code View should be able to show resizable image.
- Implement issue 2038: Spellcheck "change selected word to" should remember sorting order.
- Implement issue 2043: Spellcheck should allow case-insensitive sorting.
- Implement issue 2029: Save and open should warn if HTML files are not well formed.
- Implement issue 2009: Add semantic tags to filenames in reports.
- Implement issue 2028: Special characters should work in non-html files.
- Implement issue 2027: Upgrade Boost to Boost 1.53.0.
- Fix issue 2069: Work around for archives where filenames are not utf-8 encoded.
- Fix issue 2068: ZIP general purpose bit 11 (utf-8) filename not set.
- Fix issue 2061: Language code using wrong character to separate country code.
- Fix issue 2057: Text selected across lines using Ctrl-F cannot be found with Find.
- Fix issue 2036: Mark for Index can insert HTML tags into code making it invalid.
- Fix issue 2041: Preview does not sync cursor after using Sigil for a while.
- Fix issue 2030: The   character is incorrectly converted to space on open.
- Fix issue 2035: Index Editor entries with nbsp character don't match text.
- Fix issue 2016: Find with wrap off and All HTML Files still wraps on last file.
- Fix issue 2001: Spellcheck does not always highlight a word the first time.
- Fix issue 2017: Clips pasted into some windows does not work correctly.
- Fix issue 2008: Index adds extra comma in some cases.