This is actually one of my favorite books. I thought this title would be my first upload, but fortunately for you Dr. Drib beat me to it.
The Spanish title is
Naufragios (Shipwrecks), which in my opinion sounds way better.

Cabeza de Vaca was a member of
the Narváez expedition. The crew initially numbered about 600, but only 4 survived. One of them was Cabeza de Vaca. In Cabeza de Vaca's own words, this book is "an account of what I learned and saw in the ten years that I wandered lost and naked through many and very strange lands." He was the first white man who explored several regions of what today is the southern US: Florida, Texas, New Mexico... In his years among the native Americans, he became a slave, a medicine man, a merchant, and even an idol.
This book was first published in 1542, decades before
Don Quijote and several years before
Lazarillo de Tormes, which means it was written way before the first steps of the modern novel. Cabeza de Vaca's narrative is sometimes awkward and frustrating, but it is still fascinating to see his personal evolution, from a very Catholic and pious Spanish nobleman to a defender of the Native Americans.
Of course, bear in mind that Cabeza de Vaca lived in a period in which Europeans were not, to put it mildly, very open minded

, so you might find some passages that are offensive to our modern sensitivity. Still, if you consider his historical context, I think you might agree with me: he was actually a very cool guy. After his return to Spain amd the publication of this book, he was appointed governor of Río de la Plata. He returned to Spain in chains because he was so benevolent towards the native tribes that the Spanish noblemen became suspicious.
Cabeza de Vaca was not a very gifted writer; nonetheless, I think this is one of the major classics in Spanish literature, and it's very unjustly overlooked.
As you can suspect after all this, I highly recommend it.