From 1980: Another Star Age Essential... the novelization of THE EMPIRE STRIKES BACK.
Alan Dean Foster didn't return (in person... or as George Lucas) so Donald F. Glut picked up the gauntlet.
I guess it would be hard for anyone not around during the Star Age to appreciate just now important these things were. The gap between theatrical release and TV premiere was something like three years so, unless the movie was deemed worthy of a pre-release, you had an awful long wait until you saw it again. Books, stills, comics and soundtrack albums really were the only ways to piece together the big screen experience.