I haven't watched or finished reading this so I want to know if Jon Snow is a main part in it????

There's no main part. Both books and show follow different points of view, Daenerys, Jon Snow, Tyrion, Bran, Sansa, Arya, Catelyn, later Cersei, Jaime, Brienne etc. There's no main focus. There are major and minor POV characters, and I could say Jon Snow is one of the major ones, but that doesn't mean he's like Harry Potter in Harry Potter. For example, in A Feast For Crows, there's no Jon Snow chapter, because that book concentrates on King's Landing characters.