Akiko went missing at the age of ten — and twenty-eight years later, her body is found. Her childhood friend Tomayo has no memory of ever dreaming as a girl, and cannot recall anything about the day Akiko disappeared. The more she tries to uncover the truth, the deeper the mystery grows — and then a series of murders begins. What is the true nature of the terror lurking in the hearts of girls who never dreamed? A masterwork of long-form mystery fiction. (Kodansha Bunko)
A page turner
Thematic warnings will also spoil a bit of the plot development. If you don't like dark themes this book isn't for you, but specifics behind spoiler tag. I highly recommend checking these if you have specific squicks and icks: dodgy sexual relationships (consensual), sexual assault, pedophilia, incest, murder, suicide
Pretty much the same level as 夜警 I'd guess (same author).
I found myself going, "Do I watch a show tonight...or do I read more?" and wanting to keep reading. The chapters are short and pull you along at a quick pace. Lots of mini-cliffhangers, complicated relationships, and hinted at secrets to keep your interest piqued.
Basic plot: A woman doesn't remember any of the dreams she had as a child, nor anything that happened the day her friend disappeared. 28 years later, she meets a woman who also can't remember her childhood dreams. Then the bones of her friend who went missing turn up in the wall of an old house...
Vocabulary wise there wasn't much for me to look up - if you have a solid base of crime vocab (basic legal words, weapons, body parts, etc) and minor medical vocab you won't either. There isn't any deviation into other subjects with specialized vocabulary. The way characters talk is generally pretty standard with no dialects or other special ways of speaking aside from a tiny bit of yakuza-esque dialogue. Women in 赤川's books seem to end every sentence with わ though which does feel a bit jarring at times (at least for me).