HELLA was to based off of Ralph "Sonny" Barger's best-selling book Hell's Angel: The Life and Times of Sonny Barger and the Hell's Angels Motorcycle Club
When HELLS was announced it was introducted as being an adaption of Hunter Thompson's novel "Hell's Angels" (link)
Sometime after the original article was posted , the site made an update hinting that HELLS was going to be a new story based off of both Sonny Barger's and Hunter Thompson's different novels (..."are trying to create the fullest and most accurate representation of the group by including accounts both from Thompson and Barger"..) which would make it an original project and not the same as HELLA (which was only going to be based on one novel).