We waited until it was almost too late to see Ant-Man in a theatre. I'm certainly glad we caught it in time; it's a pretty wonderful movie.
The story: once, long ago, Dr. Hank Pym (Michael Douglas) was the Ant-Man, with shrinking powers and the ability to communicate with actual ants to command them to his will. A tragic outcome to one of his missions caused him to retire from the superhero game, and to withdraw his shrinky technology from use by others.
In the present day, Scott Lang (Paul Rudd) is released from San Quentin, where he was doing time for a Robin Hood-style caper. He struggles to make an honest living and be reunited with his beloved (utterly cute) daughter Cassie. Spoiler alert: he becomes the new Ant-Man in order to save the world from Pym's old protégé, Darren Cross, who's on track to rediscover Pym's secrets and sell them to the highest bidder.
Physics majors (like me) will need to temporarily forget their education about various conservation laws and the square-cube principle. But once you've done that, have fun. Like Guardians of the Galaxy, the movie intertwines its ostensibly serious world-in-peril plotline with abundant jokes and hilarious sight gags. This is tough to do right—even the genius Brad Bird didn't quite get it right in Tomorrowland—but it really worked for me.