thanks for the responses, everyone. most of you hit the nail on the head that it's about a D&Dish sort of game. (it's not actually D&D though, because i don't know the rules about copyright infringement regarding that, and having a fictional version of the game allowed me to tweak some of the minor rules just a bit to better fit the story)
biggest problem so far (which i recognized would be a problem when i had this idea for the cover) is the dark tone. the story is actually comic fantasy. it's about a group of guys who piss off their new game master, and he magically sends them into the fantasy world in the bodies of their fantasy characters. the black twenty-sided die is the vehicle i used for the portal. magic dice.
and while there are some dark moments, the overall tone of the book is meant to be pretty light.
but dammit i really like this cover. i even kind of like the dark tone of it. what i'm hoping for is for rpg geeks to spot the die on the cover, then recognize the reference in the title, and be interested enough to give it a shot. and then when they start reading, they think "whoa... this is totally not what i was expecting, but it really kicks some ass."... and then tell all of their geek friends about it at their next gaming session.
too much to hope for?