What do book editors really do?

Im a freshman (technically sopre if you count credits) in college. Its my 2nd semester and until now I have been an education major but the moe I think about it the more I wonder if I shouldnt be doing something with reading and books and writing when I get older.I love to read books and there is this weird feeling of excitement and anticipation when I go to book stores. If I did want to do that what should I then major in that would make me marketable there, english? And after that what else should I do, I/'m sure thats a hard field to get into so if anyone has any dadvice I'd love it.