I haven't read the Walking Dead comics yet. Would playing the games by Telltale give away much, or do they have a different storyline?
It is a completley new storyline. You can read from this link-
...a game spanning five monthly episodes that tells a new story in the Walking Dead universe while staying true to the grim tone of the comic books.
Also, if you haven't read the comics yet, you really should they are amazing. The show is really good too, but it doesn't follow the comics all that well so far.