I don't know that the TV series is better than the books, but it is just fine on its own as an adaptation.
The books, if faithfully translated to screen to the letter, would result in a show that would be damn near incomprehensible and wind up running for 30 years. The average fan struggles to keep up with the names of the 257 major actors credited with roles in the show. Imagine if the cast were over 1000?
In the end, recounting the entire life histories of all 997 prior Lord Commanders of the Nights Watch or every Targaryen GRRM thought to name or all five Blackfyre Rebellions just wouldn't make very compelling TV. Of course I'd watch it, but that wouldn't pay HBO's production costs. As the show stands now there are so many threads that a given episode doesn't stay with one character for more than eight to ten minutes, we haven't seen Bran since 2014, Gendry's apparently been rowing a boat in circles off the coast of Dragonstone since 2013, and last nights events in Meereen make it feel like the whole Slaver's Bay plot line will stay a dead end until Season 8.