Literature is only really powerful if you can apply the knowledge in some productive means. You can download the entirety of publications available on Elsevier, but will only ever be able to utilize a tiny fraction given time, skill, and education constraints. You might argue that having access to a host of literature and being able to distribute said power to people able to use it accordingly might make you powerful as well, but then again, you’re more of a mailman to the ones actually wielding the power. With the caveat that you could selectively restrict access.
Fiction on the other hand has no real-life impact, but is easier to be understood by all, and might in turn spur you into action or inaction, channel creative energy, or at worst, allow you to pass time without boredom. Certainly a different level of power, but not to be dismissed either.