I should check if this is a legitimate book or if it's from a dubious source. Sometimes, repacks of books can be pirated copies or contain malware. I also need to consider the author's reputation. Let me search online for "El Mensajero de Agartha 6" to see if there's any official information. Hmm, I found some references to a serie called "El Mensajero de Agartha" by Carlos Alvarado. The sixth book might be part of this series.