Man-God by Alfredo Lopez Austin is (along with basically his entire bibliography) absolutely essential in getting a good grasp of the mesoamerican side of it, not only the religion but the culture that created, a culture that was effectively alien to western sensibilities.

Spanish public version: http://www.historicas.unam.mx/publicaciones/publicadigital/libros/hombre/dios.html

English commercial version: https://www.amazon.com/Myth-Quetzalcoatl-Religion-Rulership-History-ebook/dp/B01DY08EC8