It's not often mentioned as a reason to learn Esperanto, but the literature of Esperanto is really quite wonderful and makes learning the language well worth it. I've only read a handful of books in Esperanto so far, but it has been an excellent way to read first-hand accounts of people writing about their own cultures and experiences.
Last night I finished reading Vikitmoj (Victims) by Julio Baghy. The book is a semi-autobiographical story of the author's experiences in a Siberian prisoner of war camp after WWI. It's a fascinating glimpse into life in these camps and how the different populations (POWs, soldiers, peasants, Jews, bolsheviks, etc.) all interacted with each other. As an example, one practice Baghy writes of is a kind of "duel" that the POWs would sometimes engage in between each other. (In the book it came out that one of the POWs had been sleeping with the wife of another of the POWs back before they had been captured.) They weren't allowed weapons, so they had to be a little creative. They would draw lots and the loser would have to provoke the soldiers on one of their marches so that the soldiers would beat him (sometimes to death).
If you learn any national language, you'll be able to read people in a handful of cultures write about themselves in their own words. But one of the unique features of Esperanto is that after you learn it, you can read the works of people in cultures all across the globe without the need of a translator as intermediary. (Of course the subset of people in a culture who write in Esperanto is not representative of the general population, but it's better than nothing!) In particular, many of these works haven't been translated into English (or any other language for that matter), so you would have no way to read them otherwise anyway!