Originally Posted by Skydog
I do the same. Additionally, I have assigned a color to it that applies to the entire row, making a "have read" book easy to identify.
Coloring rows is an expensive operation for calibre, so if you have a very large library you probably don't want to do that. What would be better is to keep your "Read" column up to date, and then create a saved search that looks for something like "read:no" (my syntax is almost certainly wrong). That way when you want to filter out stuff that's not been read, you just use that search and depending on your search settings it will either highlight the matched rows (as if you had colored them, but only on demand when you run the search) or filter out all the non-matches and just show you unread stuff.