For Relationship Marketing, this is a text I read for school.
https://www.amazon.com/dp/B005S04CWE/ref=cm_sw_r_cp_apa_RtEYFbS032H03
As far as Marketing in general, I would narrow down what kind of marketing you are interested in. Communications is a key part of marketing so if you are looking to utilize social networks and media, I would see if Mass Media Communications may help.