Adding to Quoth's post above:
Create a new integer-type column, #percentread. I suggest
{0}% for format. You may want to set the default value to 0.
Install Kobo Utilities plugin. Here's the settings.
Once it's set up, you can then put this template in a 'column built from other columns' to turn it into read statuses.
Code:
program:
if $$#percentread >=#1 && $$#percentread <=#99
then 'Reading'
elif $$#percentread >=#100
then 'Finished'
elif $$#percentread == 'None'
then 'Undefined'
elif $$#percentread >=#0
then 'Unread'
fi