For a mash up, this one was actually pretty good.
I'll admit it has been a few years since I read Wuthering Heights and there are some parts that I only vaguely remember, but Gray does a decent job of seamlessly inserting vampires into the original text. At times I found myself questioning what the actual version was because the mash up story fit so well together.
I would recommend not reading the back cover of the book before starting it, because it contains a huge spoiler that really isn't revealed until the book is nearly over.
Overall, I think this was a good monster mash up and enjoyed it about as much as the original.