I had seen the film before I read the book.
Both are as good as each other, although I think maybe some people might be disappointed if they watch the film first then read the book and vice versa. However for me, since I have a very vivid imagination, I could picture the film in my head while I was reading this book.
The film/book each have a slow pace, that builds the tension.
This leads to one of the most memorable scenes in a book/film. (In my opinion, the part of the book/film at the hotel on-wards is the best part)
I love this book, and I really enjoyed reading it, for a full day, because at the time, I was really ill, so this helped a lot.
If you like Japanese cinema/culture or just Japanese or Korean Literature in general then I think you will enjoy reading this book, and watching the film. Although the pace sometimes, might be a little slow, for some people.
Personally I am a huge fan of foreign literature, especially if it is set in Japan, Russian, Germany and it involves a crime, or it is a horror story. I also really like the dark humor in these types of books, when the main character is considering doing something out of character, and thinks of it in a funny way.
I recommend this book, to fans of Japanese culture or foreign literature. I just ordered another book by this author, and I can't wait to read more of his work.