I loved the premise of the book, but the execution was terrible. I didn't find any of the main characters likeable, and the writing was somewhat amateur-ish. Seth was selfish, stupid and bratty, and Kendra was a know-it-all who doesn't get into trouble. A lot of the things that happen in the book are the result of Seth being stupid and not listening and Kendra seems to go along for the ride. Their relationship with each other was not that great either. A lot of times, they were downright mean to each other. Their grandfather was fairly irresponsible, and most of the things that happen in the book happen because he isn't upfront with the kids, wanting them to discover things on their own. Either he doesn't trust them or he thinks things are on a need-to-know basis. He even says that what they don't know can hurt them, and yet he doesn't bother to fill them in on anything. 
 That being said, I found myself wanting to know what was going to happen next, especially the last 4 or 5 chapters. I have no idea why, since there doesn't seem to be any main conflict. Where's the tension and what are they trying to accomplish? There are small conflicts which usually consist of Seth wanting to do something and doing it even after Kendra tells him not to. At the end, Kendra, Seth and their grandmother try to stop this really evil creature from destroying Fablehaven. So while there is some build-up to this, and it was pretty the book was going towards that ending, it was still annoying. 
 I found that the magical preserve was just a dumping ground for whatever magical creatures popped into Mull's head. And instead of being about caring for the different creatures taking refuge there, it was about kids breaking the rules and almost destroying the sanctuary. 
 I think the main reason why I kept reading was because I liked the idea of the story more than the actual story. I can see kids really liking it, but it just wasn't my cup of tea. 
 It gets a 2 out of 5. It's another case of good idea but bad execution.