It's an expansion upon Zeven. Just like in Zeven, the corruption is divided into chapters which each have a specific grouping of fetishes that are the focus. Though, each chapter in this game has a wider variety of fetish types per section, and many more CG to represent them. There's even animations for the heroine now. If you didn't like Zeven, you likely won't like Grace, but I would suggest giving at least the first two chapters a try just in case, as a fair bit has changed.