I prefer a Date for read ( also use Year 2000 to mark abandoned)
I also have columns for the
Count Pages PI
2 others I have T/F Verified (EPUB), where it passes the Debug part of the Editor and a date that I do (clean/tweak to my style) Edits. Blank is not done.
BTW I use tri-state T/F. T pass, F failed (not fixed) blank NOT Verified
IMHO Lean and Mean. don't make a column for something a saved search can show. Blank can have a meaning (there is a place in the Add your own columns form for notes. use it

)