The original Ant Man, Hank Pym, was introduced in the 1962 Tales to Astonish #27, while the second Ant Man Scott Lang was introduced in the 1979 Marvel Premiere #47. These are great classic books, but I wouldn't recommend you start there if you're new to comics.
I recommend the 2015 series by Nick Spencer. This is a great series in story and art, and a perfect starting point. Scott is a good-hearted guy who makes a lot of mistakes, working to get his life together. If you've seen the Ant-Man film, you have a good idea of Scott's personality and the kind of humor you'll find here.
Here is Ant-Man and Astonishing Ant-Man in reading order: