"A Scanner Darkly" is dedicated to his many close friends that suffered or died as a result of drug use. I think there is this heartbreaking dedication at the end of the novel, with the names of his friends and how they ended.

Yet the book is full of subtle humor, and a profound understanding of individuals' tragedy at the same time.

There is a great movie made after the novel, with the same name. The movie does capture the spirit of the book, even as switching the medium, a noteworthy achievement.