To me diversifying your reading life means reading a variety of genres, authors, topics, book covers. basically anything that might affect your reading choice. For example, I only like to read books that usually sad teen books with some super complicated story and people that fall in and out of love and emotionally unstable characters and blah blah blah, therefore any book that I read that is not like any of those things would make my reading choice more diverse.
I think that you should definitely read out of your comfort zone because you might find out you really like another author, genre, topic or what have you. My goals are to try to read more from authors with a diverse background and I would like to read other genres. Maybe I will pick up a sci-fi book for the sake of my future students that won’t want to read sappy teenage stories.
The link above is definitely interesting if you want to find books with a lot of different kind of genres and topics from main characters that are LGBT to characters with diverse backgrounds. Check it out!