Originally Posted by
FlashingSabre
So for Lang you'd want the Scott Lang trade, covering his origin and some important early stories for him, Avengers: The Children's Crusade, where's he's resurrected and reunites with Cassie (I'd recommend reading up on Young Avengers if you're interested in Cassie's development. She's a great legacy character), and Nick Spencer's Ant-Man run, which is his only really notable solo stuff. Geoff Johns' Avengers, Matt Fraction's FF, and the last arc of Spencer's Avengers World are other highlights, though I haven't read them myself.
For Pym, the recent highlights are Busiek and Perez's Avengers (particularly Ultron Unlimited), Slott's Mighty Avengers, and Gage's Avengers Academy. I also hear pretty good things about Avengers A.I., but I haven't read it myself. The fake skrull Hank features in Avengers Initiative, if you're curious how that went down. The whole Pymtron thing went down in Remender's Rage of Ultron, and then into Duggan's Uncanny Avengers and the ongoing Secret Empire, but I'm not a fan of that twist, so I haven't read those yet.
Hank's other major stories are the Epic, covering his debut and brief solo run in Tales to Astonish, and then various major stories throughout the first volume of Avengers, like his three major mental breakdowns and a lot of the Ultron drama. West Coast Avengers covers his recovery from the third breakdown where he hit Jan, I believe, along with some more Ultron stuff.
Fair warning: a lot of modern writers can't be bothered to actually do research on Hank, and tend to obsessively fixate on the whole "wife-beater" thing, (even though he isn't actually a wife-beater, he's mentally ill), which tends to ruin their treatment of the character. Avoid Ultimate Hank at all costs; he's a straight up abusive husband, and it's extremely uncomfortable to read stories with him. He also eats the Blob alive in Ultimatum.
Finally, the Avengers: Earth's Mightiest Heroes cartoon does a fantastic job with Hank, Jan, and Scott. It's a great way to get to the core of the characters quickly.