I didn't think it would be possible, and I really didn't want it to be true, but I have at last found a Buffy book which is mostly boring.
I recently ordered Michael Adams' Slayer Slang off Amazon, after literally years of humming and ha-ing over whether I wanted to get it, because I read a good review of it somewhere. Plus, I'm quite interested in linguistics on a layperson's level (Bill Bryson - really! - has written some great linguistics books).
Unfortunately, this book is as dry as a really effective nappy worn on a hot day.