This is not true. Most of the first 4 seasons were word for word, beat for beat with the books. The differences were the tweaks they had to make to the main story because they decided to cut out characters and their story lines. Example: In the books, Varys is working behind the scenes to help Young Griff, aka Agon VI aka Griff Blackfyre (possibly). In the show, he is working behind the scenes first for Viserys, and later Daenerys. Seasons 5 and 6 are probably closer to the 50% from the book. The other 50% is some goofy shit they wrote in to fit GRRM's outlines.