How important is the setting?

I think it depends on the book, a big part of books like the adventures of huckleberry finn and the adventures of tom sawyer was the mississippi setting and the river in huck finns case. I dont think it would be the same if those stories were re interpreted and set in space, or Detroit or something like that. Sometimes though I read a book where the setting is described so much that it almost becomes redundant, or small details become too important for example the twilight series spends too much time describing how gorgeous Edward is.

I would have to say setting is just as important as any other aspect of a story (plot, character, theme, mood, etc.), however, many author like to frolic around every aspect of a setting ad nauseam. Setting is meant to be part of the backdrop of a story, not a way to make up for lack of a good plot.
e.x. Twilight lol
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It has to depend on the book and the author

Here's the thing- using the Mark Twain examples, you can't separate what Huck Finn and Tom Sawyer were as books without the colloquialisms that he uses, and without all of the hundreds of different things that he does to paint a picture of that time and place. His books are about that time and place, and specifically how to boys born into that time in place (although into admittedly different situations) react to their surroundings.
You could say the same thing about Moore, pretty much every single one of his books intrinsically include setting into what they are about.
There are books and authors for whom it's not so important- like, for instance, Dean Koontz, whose books are more character-centric, or maybe even Douglas Adams- where setting is whatever is convenient to make whatever joke he's interested in making.
That's kind of what I think.
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some stories are free of time and place because they deal with archetypical themes.

Some stories are "slice of life" so location/time become more important, but not necessarily essential. Tom Sawyer was far less dependent on place than Huckleberry Finn. It could mostly take place in almost any small town, perhaps even today.

In Huckleberry Finn, the river is far more important than just setting. It is multisymbolic, almost a full character in the book.

When the writer takes to describing each filigree in the pattern of the wallpaper, it's a sign they're unsure on story, trying to pad word counts, or suffering from severe OCD. There are a few books that I'd love to finish, but I just can't stand to read another description of every fucking grain of sand on the beach. I get it dude, we're on an island. A good editor is worth every penny.
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As others have said, the Setting can be as much of a main character as the people, and it can also be completely arbitrary. Some examples:

Life of Pi, by Yann Martel - majority of the book is a kid on a raft floating across the Pacific Ocean. Obviously, without the setting, the rest of the book makes no sense.

Harry Potters - you could replace England with Botswana, and other than some vocabulary, it could work. However, Hogwart's (the school), is almost a character in itself, and so you couldn't just replace Hogwart's with a random prep school without having to re-work huge plot points.

Wonder Boys, by Michael Chabon - the setting of Pittsburgh comes from the fact that Chabon lived in the city for a while, and knew it enough to write it believably. Again, change the bar in the Hill District to something else, and the book could be set anywhere and still work. Pittsburgh in this book adds to the gloom and run-down-ness of the characters, however, most other US cities could be painted with the same brush.

Personally, I really enjoy dynamic and multi-faceted settings, ones that come alive and exist well beyond the words on the page. But, it's not always necessary. I would ask myself - is the setting of Chicago (my home town) important to the story? If it is, than I want to take advantage of that and weave it into the story so that they are inseparable. If the setting doesn't provide big plot points or set up conflict or provide resolution, than trying to make it a big part of the story will be a distraction.

And finally, if you want to set your movie in, say, Gary Indiana (I assume this would be of the Horror genre), but you don't *know* Gary enough to describe the streets, the hangouts, the best restaurants, the smells and sights of the city - then you might be better off having an anonymous setting, or just making one up.

Sean