Spell check dialog: Allow up and down arrow keys to work regardless of focus.

Update bundled Qt to 6.4 this means calibre on macOS is now only supported on Big Sur and newer.

Add by ISBN: Allow adding using identifiers other than ISBN as well.

calibre:// URL scheme: allow specifying a Virtual library for show_book URLs.

Note that this means that old voice, speed and audio devices setting will not be used so a reconfiguration might be needed.

E-book viewer: Read aloud: On Windows switch to using the new Microsoft speech subsystem with access to more voices.

Improve hover highlight color in tree views.

Edit book: Spell Check dialog: Fix second word not getting selected when after first word is fixed.

Fix a regression in calibre 5.0 that broke sorting the device view by title if one of the books has an empty title.

E-book viewer: Fix a regression that caused a spurious error on Windows when reading out selected text.

E-book viewer: Read aloud: Fix a regression in the previous release that caused an error when using Read aloud on a chapter with no text, such as the cover page.

E-book viewer: Read aloud: Fix a regression in the previous release that caused the Read aloud controls to not reappear when Read aloud is canceled and restarted.

Content server: Workaround for Safari regression causing bookmarks to disappear on reload.

E-book viewer: Fix some adjacent highlights with nothing in between them not being displayed.

Content server: E-book viewer: Long tapping on an image now causes it to be displayed in an internal popup rather than a new window as some browsers block the creation of new windows.

Calibre et kobo