I found out about this book adaptation after finishing the movie and it instantly made an entry in my reading list. The horror of reality and struggle shown into the movie already blown me away, and I can't wait to read the more details and gruesome version of it in the book as most of the time in book adapted movies, a good chunk of the original story get lost in the limited timeframe.
And Do watch it, I don't know how much the movie followed the original work, but in general it is a good movie.