Obviously the major plot points are similar, but there are leagues of differences between the book and shows. The characters like Arya and Sansa are swapped completely for a lot of it with Ramsay, the show never shows the "SPOILER ALERT" Resurrection of Cat. There are so many large details in the books you would think critical to a story that aren't in the show. Also, you can't really expect to get in depth into a story when you have 5 large books compared to a season of TV that lasts 10 or 7 hours. There is so much missing from the show, it makes it worth reading the books just to see all the back story and missing plot points.