Before seeing this movie (http://www.imdb.com/title/tt0305206/combined) I knew nothing about Harvey Pekar and American Splendor. Seeing the movie made me reserve some of the comics at our local library and do some googling.
The movie is subtle and slow moving with focus on describing the characters and the background of Harvey Pekar and his friends, which is does perfectly. A movie with those undefinable moments where you just smile and cannot find the words to describe the situations. Awesome music as well. 9/10 from me.
I would LOVE to see the genuine scene, where Harvey actually lashed back at David Letterman - but World Wide Pants/NBC would not allow the footage to be included in the movie.. <_<