Enumerated column is the easiest method.
My method is to have a #percentread column and then use a template to then translate that into a reading status. This is mainly becuase Kobo Utilities can populate the percentread from my device.
Here's a simplified version of the template I use:
Code:
program:
percent = $$#percentread;
if (percent >=#1 && percent <=#99)
then 'Currently Reading'
elif percent >=#100
then 'Read'
elif percent == 'None'
then ''
elif percent >=#0
then 'Unread'
fi