Certain Buffyverse authors are really good at interweaving new characters and established canon. For example, Christopher Golden utilized the character Lucy Hanover, who was mentioned in the original WB trailer for the series, but never mentioned in the series proper. And she would pop in and out as a spirit, since the Gatekeeper trilogy. And all of Golden's novels had elements carry over between the novels. And as an avid Buffyverse novel fan, I LOVED that. Because it was special for die hards who read all the books. For example, there was a throwaway line Willow said in "School Hard" about this bar near the docks called the "Fish Tank," and it appeared frequently in his novels. It just works really well when there's elements that make the reader feel "at home" when you read multiple novels by one author in the novelverse. There is almost an entire canon from just the Buffyverse novels, separate from the canon of the show. Kind of like a multiverse. Which is cool.