User blog comment:DisturbedDeaddMan/Spin-off Books Category/@comment-37434202-20190518071403/@comment-34589382-20190518135235

To sum up: We add "Spin-off" category only for books that are confirmed to be directly set in the same universe and confirmed to be spin-offs of the original series and " Sidequel" for books that are occurring and set in the same universe another book like RoE is in the same universe as TRR and share the same time frame and some places or AtV and Hero being in  the same universe and a slightly different time frame since the events of Hero happened decades ago according to the timeline of AtV.