The oeuvre of a writer or artist refers to all their work combined. Writing one book isn't much of an oeuvre, but writing ten could be.
This is a French word often used by critics — people who comment on the work of writers, painters, musicians, and other artists. An oeuvre is the total output of an artist. Just like critics give a thumbs up or down to a single movie, they give opinions on oeuvres as well. You could say a band's current album stinks, but since they've made great music for 10 years, they still have an impressive oeuvre.