Is it still worth reading the books? (No Spoilers)

I've watched Game Of Thrones till S4, and liked it quite a lot. I'm thinking of buying and reading the entire ASOIAF. While I think the series prob did cover major plot points, I'm wondering if the books has some extra content or if not, still enjoyable for readers. Also I hear S5-S8 aren't book compliant so hopefully there's a decent deal of extra content for the last book/s.