I really like
"Das Lied der Nibelungen - The Nibelungenlied" - an epic story, close to compare with
The Lord of the Rings. It is about Love,
Treachery, Friendship, Wizardry, Creatures, Dwarves...
"Faust" - it is about sense of life. Is it worth to sell your soul to get the answer? and a lot more (citisism to society, church,....)
People wrote hundreds sites about these two books above - so I try to keep is in a nutshell.

"Unterm Rad"-a story about a pupil in a boarderschool. Critisism of Church, Society, and the pressure of people around you and yourself are treated here.
"Silentium" - Murder at Boarderschool. This case seems to involve more and more people. Poor men, matchmakers, slavery, gouvernment, artsist, in
our time, in the middle of Austria! Oh, and critisism to church again.
"Ristus/Sanctum" Fantasy Book about the hunt for Lycans which last about centuries. Literally not very much worth - but it is a good book though. A before-I-go-to-bed thriller

You could compare it with hm... The DaVinci-Code.
"Die Physiker"- This is about scientist, who found out something, that would be too dangerous in any one's hand. So they keep acting as insanes.
Only southamerican I have read is Jorge Luis borges in spanish - so I have to say, it was hard for me to read. Maybe I try the german version again.