Is the TV show merely inspired by the comic series, or is it somehow tied to it in terms of story progression?
I ask this because one of the attractions of the TV show is that it breaks from typical TV formula. It's unpredictable, like life, yet if it's in lockstep with the comic, then the story is already laid out - like watching the delayed broadcast of a sporting event, the outcome is easily spoiled.
The most strict answer would be: Not really faithful
A better answer would be: It has the main point the same.
There are tremendous differences between the comic and the TV adaptation, but they haven't got off track (that much). There people that have died in the show, that are still alive in the comic and people (like Daryl) that don't exist at all in the comic.
There are many scenes, like the scene with the deadly flu in prison (last season) that wasn't on the comic. But the prison exists. The characters stay there for quite some time before the governor destroys the prison.
If you have the time and energy, I highly suggest you read the comic
Judging by the answer to this question:
Why do they change the storyline?
I'd say there is at least some difference between the comic and TV series.
Also, check out this article to see 20 differences between the TV show and the comic. Beware! There be spoilers a-plenty in the article. Also, most relate to character differences (did you know Daryl and Meryl weren't in the comic at all?), not plot difference, though some are plot-related.
"As a geek, I like to think of the television show as this alternate dimension parallel to the comic book universe." - Robert Kirkman, 2014
Events and characters might migrate in either direction, but the exact details don't necessarily match. For example, Abraham, Eugene & Rosita are basically the same people, so comic readers knew Eugene's secret in advance, but the reveal happens differently. And...
The hunter cannibals from early in the comic became Terminus in the show.
