Top Free Open‑Source EPUB Readers for Ubuntu and Other Linux Distros

Essential features of an EPUB reader

User Interface : Simple, intuitive navigation that mimics a physical book.

Customization : Adjustable font size, type, line spacing, background colour and other visual settings.

Bookshelf : Ability to organise EPUB files and track reading progress.

Annotations : Highlighting, underlining and note‑taking within the document.

Sync : Optional cloud or device sync for bookmarks and reading position.

Free and open‑source EPUB readers for Ubuntu and other Linux distributions

Calibre

Calibre is a full‑featured e‑book management suite that also includes a powerful EPUB reader. It can convert between formats, edit EPUB metadata, fetch information from online sources and create custom e‑books.

Supports a wide range of e‑book devices (Android, iOS, Kindle, etc.).

Integrated library manager with metadata retrieval.

News aggregation and automatic conversion pipelines.

Built‑in e‑book store browser.

Installation (Flatpak): flatpak install com.calibre_ebook.calibre Native packages are also available from the official website or distribution repositories.

Foliate

Foliate is a lightweight, modern EPUB reader built with GTK4 and tightly integrated with GNOME. It offers an immersive reading experience with extensive customisation options.

Immersive view with auto‑hiding toolbar.

Table‑of‑contents view and direct download from major e‑book sites.

Dual‑page and scrolling modes.

Custom font, line‑spacing and built‑in brightness control.

Reading‑progress slider, bookmarks and annotations.

In‑book search and quick dictionary lookup.

Installation (Flatpak):

flatpak install com.github.johnfactotum.Foliate

Okular

Okular is the KDE document viewer that also supports EPUB files. It provides a rich set of customisation options and annotation tools, though it does not include a dedicated library manager.

Supported formats: EPUB, PDF, DjVu, common image types, comic archives (CBR, CBZ).

Adjustable font size, font type and background colour.

Annotation tools for highlighting and notes.

Installation (APT): sudo apt install okular Installation (Flatpak):

flatpak install org.kde.okular

Bookworm

Bookworm originated as an elementary‑OS app but is available for all major Linux distributions. It offers a clean UI, customisable fonts and colours, a bookshelf and progress tracking.

Supported formats: EPUB, MOBI, PDF, EB2, CBR, CBZ.

Built‑in tag editor, rating system, search, chapter navigation and keyboard shortcuts.

Installation (Ubuntu PPA):

sudo add-apt-repository ppa:bookworm-team/bookworm
sudo apt update
sudo apt-get install com.github.babluboy.bookworm

Installation (Flatpak):

flatpak install com.github.babluboy.bookworm

FBReader

FBReader is a popular multi‑format e‑book reader. Although it became closed‑source after 2015, an SDK remains available. It supports EPUB, MOBI, FB2 and HTML, provides a bookshelf, annotations and optional cloud sync.

Installation (Snap):

sudo snap install fbreader

Koodo Reader

Koodo Reader is a newer free and open‑source EPUB reader built with JavaScript, HTML and TypeScript. It is distributed as an AppImage, DEB or RPM package.

Download page:

https://koodo.960960.xyz

Discontinued readers (reference only)

GNOME Books – source: https://gitlab.gnome.org

epub CLI reader – source: https://github.com

Comparison of key features

Calibre – full UI, customisation, bookshelf, annotations, sync.

Foliate – UI, customisation, bookshelf, annotations; no sync.

Bookworm – UI, customisation, bookshelf; limited annotations; no sync.

Okular – UI, customisation; no bookshelf; limited annotations; no sync.

FBReader – UI, customisation, bookshelf, annotations, sync.

Koodo Reader – UI, customisation, bookshelf; annotations and sync depend on configuration.