If you haven't read the book and have no expectations except a high energy action film with numerous explosions, you are good to go and will most likely enjoy this movie.
If you have read any of the books you will be seriously angry, let down and astonished at what they have done to a very enjoyable read.
Someone took an action packed book that is the introduction to a series featuring a super agent who miraculously does the impossible under impossible circumstances. He is a singleton who gets the job done no matter what. He may have help along the way but ultimately, it is the Grey Man who overcomes and wins. There are a cast of characters he interacts with and we see them throughout the books. The story line builds and broadens but always comes back to The Grey Man who excels at killing bad people.
I began watching the movie and had to stop since I was confused. They basically took 5 books and mashed them into one screenplay. The reworked characters which completely changes the story arch. They introduce characters we don't meet until maybe the 4th or 5th book and kill off characters that are important in later books. They took and awesome first book and turned the Grey Man into a shadow of himself although they did make sure to have a female agent who wins the day...annoyingly inclusive.
This ended up just being a movie with a lot of big explosions as opposed to an entertaining ride following an agent who overcomes the impossible, saves the day (with a little help along the way) and outsmarts, out guns and outfights the bad guy.
I did in the end watch the movie going into it thinking okay, it's just a spry thriller instead of "ITS THE GREY MAN". It was okay but nothing like the book and no where near as entertaining as the book.
So sad.
When you know what they started with and see what they ended up with you can't help but wonder what the screenwriter/s were thinking :(