Based on the TV show from the 1960s, and set in the early '60s, the movie follows a CIA agent (Cavill) and a KGB operative (Hammer) in a joint mission against a mysterious criminal organization working to proliferate nuclear weapons. Sex appeal is provided by the leading men, natch, but also Alicia Vikander and Elizabeth Debicki as shown in the trailer, Plus, it looks like Hugh Grant will be back in action with some pithy one-liners. Missed that from him.
All in all, Guy Ritchie's movie looks pretty promising -- or maybe the trailers are just that good. But it looks like "U.N.C.L.E." might have the right mix of action, humor, intrigue, randy innuendo, and (so important in a movie like this) bromance.