It depends on what you mean by “worth” and “it.” If you’re passionate about literature and want a career engaging in it – studying it, writing about it, teaching it – then yes, that’s the path to that career. It’s not easy, and the PhD is just the opening salvo of challenges on the way to a tenure-track job in academia. If you just want to keep a hand in literature because you like it, I recommend pursuing any other career, and fostering groups of friends who read and talk about literature. I recommend talking to people with comp. lit. PhD’s to get their perspective.