This was a pretty entertaining movie at times but there were definitely parts that could have been improved.
In terms of Marvel movie rankings, this isn't the worst Marvel movie to have ever been produced (Thor2)but it's also not the best. Instead, it's somewhere near the middle really.
So what is Ant-man about? It's the story of an ex-con who gets the chance to be a hero and save the day, with the help of Hank Pym and his daughter, Hope. They're there to stop an unstable and unscrupulous businessman from selling the shrinking technology to Hydra, even if it means they have to break into the businessman's company and steal his research. Or as Hank Pym says "I hired you to break into somewhere and steal some shit".
I found parts of Ant-man to be too draggy or stale. But mostly the exposition parts where they're really setting up the backstory of Scott, Hank and Hope. Maybe it's just the recent influx of Superhero movies and their sequels but sometimes, the hero's Origin story just seems to drag on way too long and I find myself enjoying the sequels more, since you don't have to go through 1 hour of backstory. Except for Avengers II because Whedon loves pointless drama.
However, with that being said, there are funny parts to the movie and quite frankly, it works more as a comedy than an actual super hero movie. Not that the fights aren't entertaining because it's always nice seeing Ant-man shrink and then pummel a full-sized man and throw him around. But the funny parts are pretty much what makes this film stand out more among the Marvel movie-verse. There are a lot of funny juxtapositions between the frantic battle between ant-sized combatants and what normal-sized people actually see. You can see it in one of the trailers released for the movie where they're battling on a toy train set and one of the trains is rushing towards the villain and he's gasping and rearing back in horror as it speeds towards him like a rushing locomotive. And then you see the normal view which is where you see this train moving slowly and then suddenly just topple off the rails.
Overall, it was a decent movie even if it felt like a bit of a filler to the marvel film-verse. If you're interested in the movie though, I recommend checking out the recent Ant-man comic series starring Scott Lang as well. It's pretty funny.