::appears as if from nowhere, where he was lying in wait to answer that very question::
It's a secret.
Oh, okay, fine... The Slayers anime is all one continuity, but the TV series and the OVAs/movies
can be watched separately without missing anything, due to a running joke that somehow, Lina's companions from the series and Naga, her companion in the OVAs and movies, have never met. The TV continuity is:
The Slayers > Next > Try > Premium (short) > Revolution > Evolution-R
The OVA/Movie release order is:
Slayers: The Motion Picture > Special (aka Book of Spells) > Return > Great > Gorgeous > Excellent
Finding any of it on English-friendly DVD now is a bit of a chore, afaik it's all OOP now (and frankly the picture quality of the UK/US DVDs is largely horrible anyway so I would strongly suggest
not paying over the odds for second-hand copies, you'll only be disappointed). It seems like Hulu has the first TV season, but I can't find anything else for legal streaming. What we need is for someone to licence the gorgeous looking Japanese blu-rays for release. I would pay handsomely for an English-friendly version of
this. Hint hint, any distributors who might be reading.