My coworker has been saying they are changing a lot from the books in this season. For example, he was saying that Jamie lost his hand in a completely different way, and that John climbed the Wall differently and a few other things. Honestly I don't really mind that the book and show have diverging stories, because if I ever did decide to pick up the books, it wouldn't be as if I was reading the same exact thing as I had watched. It doesn't bother me at all if the story changes, as long as it stays as good as it has been.
Spoiler
Jaime lost his hand in pretty much exactly the same way in the books. likely even word for word.
In regards to Gendry, I feel that they are fusing 2 different plots together. in the books, Melisandre had to find a bastard of Robert Baraethon. The one she found in the books is a different child, but it's around this point that Gendry's plot stops entirely when he joins the brotherhood. So while it happened slightly differently in the books, it's more or less the exact same thing, just using an existing character who's story is over, rather than confuse things further by introducing more characters. it makes sense to me
Also Sansa's story does get more interesting. definitely more interesting.