GoT season 2 diverges even more from the books.
Game of Thrones season two exceeded our already high expectations and defied our fears. As George R.R. Martin's source material becomes more and more challenging to adapt, the TV show managed to stick remarkably close to Martin's storylines while making some elegant adjustments.
Nice walkthrough of the main changes from the book. Note that it contains quite a few spoilers, if you haven't seen it yet.