How closely does the HBO series "Game of Thrones" follow the book?

I finished watching the first season and I would like to start reading the books. It's always best to read the books first, but I can't wait to see more of the story. If the books are not very close to the show, I might not read it. Has anyone experienced both?How closely does the HBO series "Game of Thrones" follow the book?
I watched the show first and then decided to try reading the books. The first book and the show are VERY similar. The show was a perfect adaption of the books. I ended up skipping the first book because I wanted to know what happened next.How closely does the HBO series "Game of Thrones" follow the book?
It's extremely close. I watched the show and then read the book, and apart from ending at a slightly different point for some of the characters, there's almost no difference.