Angels in America is an amazing piece of theater that manages to blend many different tones while still feeling like a totally cohesive whole. For starters, it's funny all the way through; bits of comedy pop up even in the most dramatic moments. There are many deeply emotional, dramatic moments too. Nearly all of the characters go through intense life-changing events. The comic moments help lighten the mood just when the audience needs it most, helping the dramatic moments to land emotionally.
The piece is also political without sounding preachy. This is probably because all of the political discussions in the play are deeply rooted in the characters – they have a real need to voice their political views.
All of this is held together by Kushner's uniquely poetic voice. The play's language is truly beautiful in places. It's rhythmic and laced with amazing metaphors. Part of what makes Angels a classic piece of theater is the way in which it successfully blends these different tones.