The book was turned into a movie with Daniel Radcliffe.
The plot is quite interesting.
Ig grow horns. It freaked him out but worst is how it affect the persons around him. The horns seems to have a drug induce affect on the bad persons around him. To be impulsive and lack inhibition. It also used as a truth serum that person keep telling him the deepest dark thoughts.
What Ig wanted is to find the killer of his girlfriend.
This is pretty interesting. Looking forward to read the book.