Lindsay & friends decide they want to make a twilight-rip off, so they set forth to write the first communally sourced version. At the time of the videos, she was having polls/questions posted that viewers responded to in order to decide characters, plot, etc. Everything that could be decided upon structure-wise was done this way. They even created a pen name and interacted with people on various book forums. Lots of alcohol, polls, and contributing writers later, we have a finished product that is actually pretty well done for what it was. <em>Awoken</em>, available on Amazon!
It's not a series, but otherwise fits what you're interested in. https://www.amazon.ca/Awoken-Serra-Elinsen/dp/1491268727
https://www.amazon.co.uk/Awoken-Serra-Elinsen/dp/1491268727
Weirdly it's not even badly written, as supernatural teen romance novels go. There's just zero acknowledgement that the premise is insane.