Game of Thrones is one of the few TV Series based on a book done right. Of course as every transposition, it can't be perfect.
The world that we imagine while we read varies from person to person so absolutely no one (apart from the producers maybe) will be totally satisfied with the end product, but anyway it's pretty high relatives to the standards. That said if you haven't read the books, I strongly encourage you to do so before watching the Tv show. You're gonna miss a lot of interesting details and plot twists if you ignore them and just jump in watching.
And hopefully by the time you finish reading all the book Martin would have finished writing A Winds Of Winter. Right?
PS: If your mother tongue is not English I highly suggest to still read them in English. Translations miss so much of the flow of the book. Martin has a very descriptive and long writing style that doesn't get transposed well when translated. Note that you need a pretty high level of familiarity with the language since he uses a lot of unusual and specific word and phrases so you might be lost in the beginning, but don't despair. When I started reading the first book (more than 10 years ago) I had to stop and take a dictionary every few pages, now I can read almost the whole book without picking it up.