I wish I could say I recommend this, but none of the characters feel real. The siblings barely interact how siblings would, and it mostly just seems like a teenagers take on what could be a horror story. It takes a very weird occult turn, and the pictures are quite creepy. I wouldn't recommend this to children, but maybe kids that have been exposed to occult information over 11 or 12.
As for the ending, the resolution is a bit silly. It's horribly unsatisfactory, and weirdly written when it comes to a certain let's just say "contract." The child I was reading it to only really paid attention to the scary parts, but even those actually were mostly just repeats. The same dream kept replaying over and over to the exact words, so expect at least 10 or so pages of that.