I am a longtime fan of the books. In the books, the vampires can sort of stand in as any minority that might have to hide and/or come 'out of the closet'. She draws subtle links to the holocaust, civil rights, etc. etc.
But mostly it isn't very obvious.
SPOILER ALERT
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No, seriously, spoilers.
Don't look if you don't want to know.
Later on in the book series, Sookie becomes aware of Other Creatures. They are not out of the closet.
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Spoilers over.
I would say, if you really love the show and want surprises, then don't read the books yet. I saw Charlaine and Alan at Comic Con this year, and they said that the first season is basically the first book, and if they get the green light, they'll probably carry on that way to a greater or lesser degree. Apparently, the actors were asked to read the books so that they know stuff about their characters they need to know that come up later.
Some characters in the show are not as major in the books. Sookie's best friend and Lafayette, for instance, are not much more than bit players.