I think this is going to be the book that in the future when encouraging others to read the series, we tell them "Eh, just get through Ghost Story as fast as you can so you can resume reading the real series."
I give Butcher props for the cojones (it's one thing to kill off a main character and remove him from the story - it's a whole other kind of ballsy move to revamp the setting and rules for a whole book, which given the first person narrative & pov, is essentially what Butcher is doing - he's basically said "Yeah, you know my series about a wizard in the modern world? Well, this book is totally not that." ), but this seems very risky. The sample chapters I've read online are kind of dull and I was already getting frustrated with the ghost world and just wanting him to get back to life already. It's like when a TV show makes one of those digressions that just don't work and you start getting impatient for them to just get back to normal already (like the Sons of Anarchy going to Ireland). Also, it's violating the "one weird thing" rule. In the Dresden Files, the OWT is a bit more expansive, but it's still just one thing. The DF's OWT is "magic & monsters exist in an otherwise real and normal world." We can accept Butcher's presentation of the rules of magic, because we know where we stand on everything else. With this book, he's totally shaken up the rules, because now EVERYTHING in Harry's experience is "fake" and not playing by the rules. When a ghost-monster attacks, we have no idea or grasp of the scope of the threat, because we don't have the rules of ghost-world as thoroughly internalized as we do the rules of the real world. When someone shoots a gun at Harry, we know what threat is implicit in that action. When a horde of zombies chases him, or a vampire lurks menacingly, or a monster demonstrates superhuman speed or strength, we understand the threat because we know how the physical world works, and can grasp that a creature that can pick up a seven-foot man with one hand is highly dangerous. When Harry's hand gets incinerated by a flamethrower, we know that's bad and that it could have permanent ramification. What about if a ghost-villain chomps off his ectoplasmic extremity? What does that mean? If it gone for good? Is Harry's post-mortal substance reduced? Does it lessen his time available? EVERYTHING about the ghost world is complete at the whim of Butcher, which is going to make the story harder to accept.

This book is basically looking like something that only will work if it satisfies the fan curiosity engendered by the circumstances of the last one, by answering questions like "How does he survive/come back to life?" or "Who whacked him?"(does that one even matter? There are so many candidates who would want to, it just isn't the same as if a different type of character in a less violent story got shot) or "What's happening with X character now that Harry isn't there to Z?" I'm going to get it as soon as possible, but I'm not holding out a lot of hope.