The perception of reality is actually the mockery that Miguel de Cervantes Saavedra intended to emphasize in the story of Don Quixote. This is a quite tri-dimensional story, almost magical, which has led to countless of thesis and dissertations on how the reader becomes "quixotized" by ending up trusting Don Quijote more than his former self.
The perception of reality is portrayed in two very important ways. The first, is through Don Quixote's eyes. He has read countless of chivalry medieval novels and has become absorbed with them to the point that he had stopped eating and sleeping and his brain "dried out". However, that is not a counterargument that what he felt and re-created in his mind was NOT true. After all, the stories were real to him. And to Sancho. So, why not accept that he had a point?
He attacked the mills thinking they were giants. He donned upon himself a rusty old armor shield. He declared Dulcinea del Toboso as his damsel in distress. He even declared sancho and his burro as his steeds. He made all that happen! True. His perception may have been outdated...but didn't it fulfull a purpose which he very well trusted?
One thing to remember is that Cervantes based his mockery upon chivarly on the writings of El Cid Campeador. El Cid is quite cheesy for the modern reader and reflects the mentalities and feelings of the early Middle Ages reader. Cervantes was literally doing the same thing as futurists as Jules Verne did which was to challenge the traditional ideas and satirize them.
For this reason you will see that ,in El Quijote, there is a lot of satire, sarcasm, irony, mockery and comedy that can be fished out of the delicious baroque vocabulary.
Hope this helps!