That's simply not the case with the ASOIAF series, I watched both Season 1 and 2 first and then read the books in the year interval between season 2 and the upcoming season 3, I can tell you that the series is in no way disappointing after reading the books, they compliment each other well, infact I actually understood more in the show after reading the books and when I re-watched the TV series I got more enjoyment out of it by knowing more about what was going on.