Sumatra PDF is a PDF, ePub, MOBI, CHM, XPS, DjVu, CBZ, CBR reader for Windows

Change line width on epub files

It would be convenient to change the line width of epub files.

There is a reason that blogs and scientific papers don’t spread their text all the way across the screen and it’s because it’s hard to read since your eyes have travel such a long distance, then back, and repeat. It’s also easier to get lost in the text that way.

They instead choose to constrain the text into a smaller single, double, or triple column layout.
Would it be possible to do something like this for epub files?

Histerically ebook screens are one hand wide say 4 inches (and could vary between manufacturers products) also ebook formats did not expect to be viewed on 50" or more screens, however the text is designed to re-flow to fit the working width, thus a user can set the width of their window to suite their preference.
Modern ebook applications such as SumatraPDF will allow for “Two column” working, in either mode.