ICO: Castle in the Mist (Haikasoru) - Miyuki Miyabe
To be fair, I was warned about the bad traits of this book, and again, to be fair, I borrowed it from the library anyway. After the main character enters the central part of the book, we automatically lose the rest of the established cast, which, I think, gave the beginning of this book its real bite and made it a different beast than the video game it is based off of.

To keep this short, the main downfall of the book itself is that it is based off of a video game in which, in order to remain true to the story must keep dialogue, if any, to a minimal. Although the use of a minimal amount of dialogue can and has been done before, the author has not accomplished it here. When we get further in, the main character speaks little and does a lot - which can be great for a video game that has other avenues through which to tell the story, but in a character-driven work of written fiction comes off like a terrible idea. And, frankly, it seems that way.

My advice would be to read until the secondary characters leave the main character and no further than that, and to only do so if you are an adamant fan of the original game.