[dwig]

Two points:
1. This is not a "recipes" issue. It should be posted under the "Library Management" sub-forum. Perhaps a moderator will move it.
2. calibre can handle this fine. There are two ways: one is to repurpose an existing column and the other is to create a custom column.

Most users with this need seem to like creating a custom column to store a marker for read and not read, sometimes adding addition status options. Personally, I find no use for other people's Ratings so I simply use the rating for my personal rating with no rating meaning that the book is unread.

I have an assortment of Saved Searches and Virtual Libraries that then use the Rating column, often in combination with other columns or Tags. I can thus quickly find a "Science Fiction" "Short Story" that is unread (rating=0).