La Guitarra de Son, Un Método Para Su Aprendizaje En Diferentes Tonos, Libro Primero Edición Digital 2021 is the final revision of the book, and was released freely to the public by one of the authors. You can obtain it from his website here: https://www.lamantaylaraya.org/?p=2592
However the audio tracks are a bit difficult to follow on the website, so I downloaded them and organized them, including all the information in the tags. You can download the tracks and listen to the audio here:
https://drive.google.com/file/d/1_HyQ6YsWC8f51ou0_BoDC1H5xibiPrgG/view?usp=sharing
Xarocho 