0.1.0
The first release. calibre with a modern look and a few rebuilt parts, installed beside calibre. Released September 19, 2026, on calibre 9.14.
It is the same program underneath. The same libraries, the same plugins and the same conversion engine all work as they do in calibre.
It installs beside calibre rather than over it, and keeps its own settings. Libraries stay in calibre’s format, so calibre can keep opening them too. Just not both apps on the same library at once.
A new look
Section titled “A new look”- One set of numbers behind everything. A colour ramp, a radius scale, a type scale and one density. A button, a menu row, a field and a tab share their padding and their corners.
- Six colour schemes. Neutral, the default, plus stone, zinc, olive, mist and zen.
- Match system, light, dim or dark, switched from the toolbar without a restart.
- Primary and destructive buttons look different because they do different things.
- Chevrons in place of Qt’s arrow triangles, and rounded windows behind rounded menus.
- All 179 of calibre’s main icons redrawn as line icons from the Tabler set. They take the palette colour and change with it.
- Inter for the interface and Literata for titles, both bundled so the app looks the same on every computer.
Rebuilt parts
Section titled “Rebuilt parts”Some of calibre’s widgets draw themselves, so a theme cannot reach them. These parts sit in front of them instead, and everything underneath is still calibre’s.
- The filter panel. One screenful of rows at a time, a count beside each value, and a Reset that clears them all.
- A preview above the book list. The selected book’s cover, title, details and actions, with the search bar and a Grid and Table switcher below it.
- The book list as a table. A Details column with the cover, title and author on a tall row. Sorting, editing in place and the header menu stay calibre’s own.
- Three cover grid sizes, default, compact and tiny. Every cover is cropped to one shape so a shelf has a straight edge.
- A rebuilt status bar. It shows the library, the sort, the counts, the device, whether the content server is sharing, and any job still running.
Help and updates
Section titled “Help and updates”- A short welcome walks through the three things that moved, with a recording of each.
- Report a bug in the status bar opens a GitHub issue with the boring details filled in. It also offers Reddit and a way to copy the details.
- Crash reports are yours to send. When Calibre Zen’s own code fails, it shows exactly what would be sent before anything is.
- An update check once a day, against Calibre Zen’s own releases rather than calibre’s.
- The features menu, under the Calibre Zen mark on the toolbar, turns each part on and off.
For the curious
Section titled “For the curious”Switches
Section titled “Switches”Each part has an environment variable that gives calibre’s own version back.
| Part | Variable |
|---|---|
| The whole look | CALIBRE_ZEN_STYLE=0 |
| Filter panel | CALIBRE_ZEN_FILTERS=0 |
| Preview and table | CALIBRE_ZEN_CENTRE=0 |
| Status bar | CALIBRE_ZEN_STATUS=0 |
| Line icons | CALIBRE_ZEN_ICONS=0 |
| Welcome pages | CALIBRE_ZEN_ONBOARDING=0 |
| Update check | CALIBRE_ZEN_UPDATE=0 |
A few take a name instead. CALIBRE_ZEN_SCHEME picks the colour scheme, CALIBRE_ZEN_FONT the interface font, and CALIBRE_ZEN_GRID the cover grid size.
How it stays out of calibre’s way
Section titled “How it stays out of calibre’s way”The app is named calibre-zen inside, and everything that name decides is separate from calibre. That covers the settings folder, the cache, the lock that allows one copy at a time, and the desktop and bundle ids. On Linux and Windows the command line tools get a zen- prefix, like zen-calibredb, so both apps can be on your path.
Known gaps at the time
Section titled “Known gaps at the time”- The Windows packages were not signed, and the installer still showed calibre’s banner.
- Windows had no handler for
calibre://links, so those opened calibre when it was installed. - The app could not install an update itself. The notice pointed at the release.
Installing
Section titled “Installing”The packages were calibre’s own 9.14.0 builds with Calibre Zen laid over them.
- Windows. An
.msithat upgrades in place, a portable installer whose folder keeps its own library, and a.zip. - macOS. A
.dmgfor Apple silicon and Intel, signed and notarized. - Linux. A
.txzfor x86_64 and arm64.