Because it's getting a new cover. Yes, Wuthering Heights has been repackaged for those teens who really want to read their favorite character's favorite book. There's a lot of chatter online about the new cover, some positive and some not so (see the comments to this post for a lovely example of the two sides to the debate). What do you think about this re-branding? Is such a blatant association with Twilight a smart promotion or a cultural dumbing down? And while you're pondering, check out this slide show of past Wuthering Heights covers.
Finally, I couldn't post about this without mentioning Bella's Bookshelf, a blog "dedicated to discussing the classic literature Bella Swan Cullen mentions through the course of the Twilight saga." Check out their discussions of Wuthering Heights and Eclipse.