The Auckland Allies series, complete in one volume, annotated by the author.

Auckland, New Zealand: a city dotted with extinct volcanoes, which can be used to anchor powerful magic. That's exactly what the sinister Blokes in Black want to do, and since nobody else is stepping up to stop them, an underpowered, bickering group of magical nobodies is stuck with the task.

Sparx: Huge nerd. Minor electromancer.
Tara: Angry artist. Also martial artist, kind of, a bit.
Steampunk Sally: History fangirl. Can see a few seconds into the future if she squints.
Dan: White knight. Demons expert. Has a van.
Lynn: Giant Buffy fan. Giant brain. Tiny sense of self-preservation.

Follow this assorted group as they learn to work together to battle demons, ghosts, body-snatching Nazi sorcerers, werewolves, and the Guardians (part cult, part supernatural vigilante force, part bureaucracy; no sense of humour about any of it).

Contains:
Auckland Allies
Ghost Bridge
Unsafe Harbour
Wolf Park
Memorial Museum
Author's annotations