According to the bottle, it is 100%
Beet Neutral spirits (they probably use grain, now) and won the 1987 and 1989 Gold Award from "The International Wine and Spirit Competition." I also found a listing for another award in 1993.
Go figure.
It was promoted for a limited time by coming in a hinged black wooden coffin with the logo painted on the top. As for the taste, it is a rather smooth vodka but not really worth the high price they were charging for it (not sure what it costs today, but back in 91-92). Its biggest selling point is the name and the conversation piece it becomes sitting on your shelf (especially if you have the coffin).
The brand also sells other hard liquor as well as once (still?) a brand of cigarettes featuring the logo on the black box and printed on each cigarette. (For a cigarette with a name like Black Death, they were fairly mild.)