I'm not sure I agree. I don't hate these covers. They amuse me a bit, and I'm not sure they'll work, but they are part of a long and --can I say it?-- venerable tradition of repackaging the classics for a contemporary audience. In grad school I knew someone who had a great collection of pulp fiction which included a pulp-y cover of Pride and Prejudice that was, for the purist, far more offensive than this one. (And much more of a bait-and-switch, if you ask me.)*
The thing is, no one's going to read these books just because of the covers. Sure, they may check them out of the library or buy them because of the covers, but once they crack open the book and start the first page, it still says "It is a truth universally acknowledged..." (Or, in the case of Frankenstein, the far-less-arresting, "To Mrs. Saville, England...") In the end, it's Jane Austen and Mary Shelley inside those covers, and that's what will (or, perhaps, won't) hook the reader. If it takes a little extra marketing to get to some of those readers, I'm not sure I'm opposed.
*I've just searched for this and can't find it, but I know I saw it once. Here are a couple of others, though, that don't strike me as much better than the new one above.