I didn't like Jazz. She was nasty to Nick, her on-again, off-again lover of the last 300 years; nasty to Irma, the ghost tied to Jazz's car; even nasty to the bat who is her escort to the correct room to do her research in the library. She doesn't do her share of the grocery shopping, but eats everything her roommate buys. She even whines when her roomie asks her to pick up a computer part for him.
My second problem was that there wasn't an explanatio of the mythos of this book in prose, or conversationally between characters, or in any other manner. For example, Jazz has animated bunny slippers which eat everything in sight including her roommate's signed Grateful Dead tee shirt. Is this a universe in which inanimate objects spontaneously come to life, did Jazz hex the slippers, did another witch hex them and give the slippers to Jazz as a present? Who knows?
Unlikeable heroine, and not enough background material.