Well, the 2 Reiman recomended are good, even Saramago is from Portugal, he has a perfect knowledge of Spanish. With García Marquez you can learn the way Spanish is spoken in America.
If you want some Spanish wraiter Ruiz Zafon with "La sombra del viento" gained a great reputation as his started out of the comercial net.
But to recommend something most especific i need to know what are you interested in, or what kind of books you like reading .