The firmware comes with built-in stylesheets which set the default styles for books according to the reader's preferences, and can in some cases override the styles set by the publisher in the book. There are separate stylesheets for EPUB and KEPUB books.
In an ideal world, the publisher would respect the defaults set by the device and only override those styles which shouldn't follow the reader's preference. For example, the publisher should let the reader choose the line spacing for the main body of text, and only override the reader's preference for special elements such as headings, dropcaps, etc.
But in practice there are many books where the publisher overrides the default settings to force their particular choice of line spacing or other style to be used throughout the book. So when designing the built-in stylesheets, the device maker has a choice:
- Take a light-handed approach: Just set the reader's preferences as defaults, and hope the publisher will respect them.
- Take a heavy-handed approach: Force the reader's preferences to override the publisher's, on the assumption that the publisher will not respect the defaults.
The main problem with the heavy-handed approach is that it overrides both the good and the bad choices made by the publisher. For example, forcing full justification might also affect some headings or images that should be centred.
In general on Kobo devices the EPUB reader takes the light-handed approach (with a few exceptions), while the KEPUB reader takes the heavy-handed option (again with a few exceptions).
There are a number of patches that can modify the EPUB or KEPUB built-in stylesheets to use the heavy-handed instead of light-handed approach, or vice versa:
Patches to use a heavier hand:
- `Force user line spacing in KePubs`
- `Force user line spacing in ePubs`
- `Enforce user line spacing and justification in ePubs`
Patches to use a lighter hand:
- `Un-force font-family override p tags (std epubs)`
- `Un-Force user text-align in div,p tags in KePubs`
- `Un-Force user font-family in KePubs`
No amount of patching will give ideal results in all situations however, so I recommend readers take control of their reading experience by learning a bit about CSS stylesheets, removing DRM, and using tools such as Calibre to fix the publisher's bad choices at the source.