My Grandmother who is 93, reads a book every 1-2 days. These are mostly Tom Clancy type novels, but she reads everything.
I go thru spurts where I will read several hours a day for weeks, but then not read for a few months. You also have to keep in mind the length and difficulty of the reading. A Kurt Vonnegut book I can often read in one day. A book such as Tale of Two Cities I think I read in like 10 days. I have also read Les Miserable and War and Peace- each of these endeavors took months.
When you read 100+ books a year, I think that you are so focused on what you are reading next you don't absorb what you are reading, and how can you when you read it that fast?
I want to read this novel, but I feel like the movie spoiled it for me. I would much rather prefer to read the book first. If I read it now I'm going to picture Javier Bardem and Josh Brolin, as well as whatever opinions I have already formed about the characters and the plot.