Is Nahjul Balagah a book of Shia belief? Is it permissible for a Sunni to read it?

I just downloaded the pdf of Najhul Balagha which a book regarding to the sermons of faithful Imam Ali(RA). I want to know is it a book for Shia sect. Not saying Imam Ali is only for Shia. Just out of curiosity asking because, Shias talk Hazrat Ali mora than anyone Also will I be sinful if I read it? Is there any possibility that I might get diverted to some false faith if I read this?