This is a book that makes you think. It uses the device of unreliable narrator extremely well as I spent a lot of the story wondering how much of the fantasy element is real or Mori's way of dealing with the death of her sister. Loved all the sf/fantasy references and was pleased with how many I got/had heard of. The sf club meetings in the library after hours amused me as they're just like the meetings at the club I go to. 
 Be warned though, because this isn't written in chapters but in 'diary entries' it's very easy to just think you'll read one more and then suddenly it's way later than you thought. Definitely a book I'd reccommend.