The book was a clever and fast read. It was described well by one critic as, "It’s a “popcorn movie” of a book, one that you enjoy mainly for its entertainment value at the time and probably won’t remember for much longer after the fact." I read it just outside Herefordshire this Spring at a UK training facility. Perfect setting for historical intrigue.
It did blend an actual biography and its requisite tone with a mythical biography and make them appear seamlessly integrated. It did not include the Washington Monument or flash.
So if you choose between the book and film, I would take the book. Seeing the trailer, it pales with the book.