This is one of the times to reiterate that I grade partly on an idiosyncratic curve determined by author, genre, and an elusive sense of whether or not the book fulfilled its own purpose.
I believe that Pin's purpose is to be 1) disconcerting and 2) weird as shit, and it succeeds on both fronts.
This is the story of Leon and his sister Ursula, children raised by a germophobic mother and a somewhat distant father. Their father, a doctor, had an anatomical model in his office--the children named the model "Pin," after Pinocchio--and used to have faux-conversations with it, basically using Pin to talk to himself. He could throw his voice to have Pin "answer" him, and he also used this trick on occasion with his patients, especially the children, on the theory that children find it reassuring to have a life-sized clear-skinned dummy with visible brain matter, veins, etc. spookily talk to them. Surely a misconception, but one aided by his own children, who are fond of Pin. "Naturally," the good doctor therefore uses Pin's voice to explain the birds and the bees to them, something that will obviously lead to amazing mental stability and sexual health.
The doctor is weird. But he's on the eccentric side of weird. His son, on the other hand, is on the "sit staring at Pin for hours" side of weird, the "I was told to stop talking to this anatomical dummy but I won't" side, the "I believe that I have secret conversations with Pin" side. And unlike his sister, he never grows out of this belief in his semi-imaginary friend. Instead, the belief deepens into a warping fixation; after the early death of their parents, Leon insists on moving Pin to the house, bringing him to their family dinners, making him his own cocktails, etc. He's decidedly troubled by the way his sister wants a life outside of the house and outside of him and Pin--something, he thinks, has to be done about that.
Neiderman does a great unreliable narrator, and Leon's perspective is really chilling in its total insularity, lack of empathy, and disconnect from reality. The appearance of Ursula's boyfriend is welcome to us, if not to him, but what's really great is when you get to actually overhear--via Leon's eavesdropping--a conversation between Ursula and the boyfriend that's not automatically filtered through Leon's skewed view of the world. That much-needed reality hits like cold water, jarring you out of the book's creepy dreaminess. And in general, Ursula's characterization, with her thoughts often clear to us even though they're inaccessible to Leon, is well-done. This is a more successful novel for me than Neiderman's Brain Child, even if the premise isn't as automatically terrifying.
This book is a dark, weird, depressing cocktail of incest, distorted sexuality, and insidious insanity. It's enough to make me have reiterated multiple times over the last few days that when I have conversations with my pets, I don't actually think they're talking back to me. Really. Promise.