The synopsis describes the book as the "remarkable story of how Brazil's biggest musical act came to sell over 20 million albums worldwide. From their beginnings playing music that could have seen them arrested, through three decades of success, struggle and strife and including new details about members leaving,

"Relentless uncovers the story of one of the world's most influential metal acts. Written with the support of the band, it is illustrated with over 70 photos, many from the band's personal archives, and most previously unseen.""