I was rummaging through my stuff and found this ad I clipped from the October 30, 1980 issue of Rolling Stone.
Of Mice and Magic came out in Spring 1980 (I don’t recall the exact publication date), originally in hardcover from McGraw-Hill. It was issued as a trade paperback by NAL in October 1980, updated in 1987 and hasn’t been out of print since.
I still can’t believe the publisher took out an ad in Rolling Stone! Considering the state of animation back then, I can’t believe they advertised it at all.