Any difference with: This is an excellent content.?
"a/an" can't be used with the word "content", it is uncountable.
I guess it is both countable or uncountable. I have two contents in my book - titles and pictures.
Content is singular, contents isn't an english word. You should say my book contains content there are pictures and titles.
Contents is an English word. If you look at the contents of a book, you'll get an idea of what's in it.
מצוין can be translated as "great" also