After the death of his girlfriend at the hands of terrorists, Mitch Rapp is drawn into the world of counterterrorism, mentored by tough-as-nails former U.S. Navy S.E.A.L. Stan Hurley. Action,Thriller Books are NOT movies. This needs to be said over and over, because there is always a cabal of complainers who hate any movie that doesn't faithfully follow its hardcover source. I haven't read Vince Flynn's American Assassin, and I don't intend to. But I feel fairly confident that he wasn't writing a movie. American Assassin (the movie) is a film-telling of the original story; it is NOT the original story, and it doesn't pretend to be. (Memo to Vince Flynn fanatics: Don't go see it.) American Assassin is a terrific watch, if for no other reason than seeing Dylan O'Brien nail it. And he is well aided by his supporting cast, most especially Michael Keaton, Taylor Kitsch and Saana Lathan. (I would like to have included Shiva Negar, but her character is severely compromised by problematic writing. She did the best she could with what she was given.) The script is larded with clichés, but for the most part the actors make good use of them. Director Michael Cuesta keeps it all moving right along. Most of the characters are very thinly drawn, leaving the actors to flesh them out as best they can. The special effects range from absent entirely to overdone. The script itself lurches from event to event, with an ending that goes beyond credulity. None of this matters. Dylan O'Brien is on screen ninety percent of the time, and his character is spot on. He is totally in command, and his charisma is entirely in charge. For a movie such as American Assassin, that's what it is all about.