I'm afraid I have to disagree with all the other reviews here. Yes, the central idea is fantastic - but what about the writing?
The first half of the book, in particular, is terrible. I found it impossible to `see' the action happening, and to get into the world of the story, because the author failed to paint a picture of anything - settings, characters, situations etc. I'm not someone who likes a lot of description - I just need to be able to visualise things. For example, a crucial crime scene is described as a room up a staircase in Ariel College - `a room bustling with people' - and that's it. In my mind's eye I imagined some sort of common room, but later discovered it was a bedroom.
There was a lot of this kind of confusion. I assumed that the body Denison and Weathers looked at in the first chapter was that of Amanda because the investigators kept asking people about their relationships with her - but I later realised that Amanda died years earlier.
This bit of text illustrates the general confusion created by the bad writing throughout the book:
`...Parrish was sitting on the last step of the victim's staircase.'
`So either he saw the killer...' said Denison.
`... or he is the killer,' finished Ames.
`Not necessarily,' protested Halloran... `The rooms on the south side of the building have windows out into the street.'
`Or,' said Weathers. `The killer could have hidden...'
At first I wondered what relevance the windows had to this character maybe being the killer. Then I realised that the `Not necessarily' speech by Halloran is a real howler of a non-sequitur. To correct this, the remarks by Denison and Ames need to be switched (`So either he is the killer...'/ `...or he saw the killer')
The characters are one-dimensional and I didn't care about any of them. The writing often descends into clichés (e.g. the room that was `bustling with people'; colour `draining away' from faces) and there is absolutely no sense of menace until right at the end. I felt the author really got into her stride only in the last few chapters - and even then, the writing wasn't great.
I did enjoy the little bits of psychology that pepper the book, and the twists in the plot, but otherwise it was a chore to read. Presumably the publisher was `hooked' by the premise and so was able to overlook the flaws in the writing, but as a reader I need to be pulled into the story's world if I am to enjoy it, and I can't think of another book I've read recently that failed so spectacularly to do this.
Sorry to go on, but in view of the overwhelmingly positive reviews here (which persuaded me to buy the book in the first place) I felt I had to explain my measly one star!