User blog comment:DisturbedDeaddMan/Spin-off Books Category/@comment-3452092-20190517213754/@comment-3452092-20190517214957

Yeah, that's probably true. Considering Olivia's linage and the country itself's history, I think that is fair to say it is a spin-off of both series.

I guess technically you could call Endless Summer a spin-off of Rules of Engagement, too, considering the whole Blaire/Grace thing. I think it probably was a "back door pilot" of sorts.