I adored this book. It wasn't in any way what I thought it would be, but I loved it for what it actually is. The most important thing to realize before reading this book is that it really shouldn't have been a young adult book, it should have been middle grade. 
 The characters are fascinating. While the setup of children with supernatural powers is not all that original, the overall world Riggs has built is one-of-a-kind. The "mystery" of the house is explained early on, but the real mystery is about Jacob himself. The photos add so much to the story, as well, seamlessly integrated into the tale to bring the characters to life. 
 (view spoiler)[But the truly fascinating part of this story to me is its relationship to actual history. I have a soft spot for Jewish history, and Riggs has created a metaphorical parallel with the actual Holocaust, the persecution of Jews, and the "hollowgast," the persecution of peculiars. He even extends this by using the school as a safe haven, much like Israel, which is then violated by those that would persecute the peculiars. (hide spoiler)] 
 I recommend this book to just about everyone. But just know going in that it's not as creepy as it appears to be on the cover. Certainly there is some abnormal imagery and some creepy bad guys, but it's relatively benign. It would be perfectly appropriate for kids 10 and up.