reading order for Buffy novels

I've just started reading Buffy fiction and I'm wondering whether it is important to read the books in order. do any books assume the reader has knowledge of preceding books, or do they only make continuity references to TV episodes?

Not really important, no, but they will assume some familiarity with the basic characters.

Remember that some of the books are versions of the tv episodes.

I know all the characters from the TV series, are there any recurring characters who appear only in the novels?

or are there any continuing story arcs in the novels (other than the obvious trilogies)?

I'm not really interested in novelisations of TV episodes, only in new original stories.

Not as far as I recall, no. There are a lot of books though, well over a hundred. I certainly haven't read them all. :)