The letter is a history and a denunciation, a plea and a work of ethnography. More than anything, it is a defense of the Andean Indians and their culture. The work is divided into two parts.
The first part, the Nueva Coronica, is mainly a history of the Andean Indians up to the arrival of the Spanish and a description of their customs and religion. Religious themes and a brief "history of the world" also appear here.
The second part, the Buen Gobierno, depicts the suffering of the Indians under Spanish rule and gives specific suggestions for improving the governance of Peru.
As far as is known, the King of Spain never received Poma's letter. In fact the letter disappeared from sight, until it was discovered in 1908 by the German scholar Richard Pietschmann at the Royal Library of Copenhagen. Andean scholars and historians applauded the find, and have incorporated Poma's drawings liberally in their books. The reviews of Poma's writing are more mixed, with complaints common about the "execrable Spanish" and the "long, rambling, and confused account." (Brundage, page 321).
I would argue that our confusion results from the differences between Western culture and Poma's Andean culture. See "The Hidden Logic of Guaman Poma".
" ...I lacked all written evidence and had to rely on the coloured and knotted cords [quipus], on which we Indians of Peru used to keep our records. Among our people I also sought out the oldest and most intelligent, on whom I could rely as witnesses of the truth." (Guaman Poma in Dilke, page 19.)
"In my work I have always tried to obtain the most truthful accounts, accepting those which seemed to be substantial and which were confirmed from various sources. I have only reported those facts which several people agreed upon as being true." (Guaman Poma in Dilke, page 20.)
"I have never been in a position to study any documents or texts and that is one reason why it has taken me thirty years to complete my work. During that time I have lived the life of a poor man, sometimes even a shivering and naked one without a grain of maize to eat." (Guaman Poma in Dilke, page 228.)
"I chose the Castilian tongue [Spanish] for the writing of my work, as our Indians of Peru are without letters or writing of any kind, and I had to translate into Spanish the phrases of the different languages and dialects which we speak, such as Aymará and Quechua." (Guaman Poma in Dilke, page 20.)
"I have given greater clarity to the text by means of pictures and drawings, knowing Your Majesty to be greatly addicted to these. I have also wished to alleviate the dullness and annoyance likely to be caused by reading a word so lacking in ornament and polished style..." (Guaman Poma in Dilke, page 20.)