Why do we read just tales in Esperanto?
A beginner reads only easy readings. A tale is not difficult, but I don't like tales very much. (I'm too old for it :) I've practised Esperanto various readings like Wikipedia, easier articles, Esperanto grammar. Now I discovered a good reading: The Bible in Esperanto. Furthermore Zamenhof translated himself the Old Testament:
La Sankta Biblio
I found some of the writings of Claude Piron interesting to read when I was learning Esperanto too. There are detective novels for post-komencantoj, but he also wrote opinion pieces on psychological attitudes to Esperanto which are very interesting. Some of his work is available here:http://esperanto.org.uk/eldonoj/piron/
Yes, I have read a few of them, and I don't really like crime novels usually. The author has a great way of 'playing' with Esperanto words that teaches you how to make good use of the prefixes and suffixes in a way that no course ever can. He makes the language really come alive!
Of course, a tale can be valuable too, but the Bible is one of the main value of our human culture. It is worth to read it in several languages. The beginning of the Old Testament is a very clear and simple text:
1 En la komenco Dio kreis la ĉielon kaj la teron. 2 Kaj la tero estis senforma kaj dezerta, kaj mallumo estis super la abismo; kaj la spirito de Dio ŝvebis super la akvo...