Paperback: Too Many Curses by A. Lee Martinez, 2008, 9780765318350.
I read Gil's All Fright Diner shortly after it came out in 2005 and thought it was really great. I read several other Martinez novels after that and then got off track. This novel was weeded off the library shelves within the last year or two so I bought it.
My advice: skip it and read Gil's All Fright or Nameless Witch. This has character after character and doing thing after thing and it was too much. Sure, I finished the novel but had to tune out each new character who popped out.
Short version: Nessy is in charge of Margle the Horrendous massive and magical castle. Margle is truly horrendous and over the centuries has populated the castle with the ghosts and trapped souls of those he has killed. A few thousand different spells and curses keep things together. When Margle is killed through his own misadventure Nessy is left to take care of things. Nessy is a bit obsessive compulsive and wants to keep the castle and all her pals running smoothly.
Longer-ish Version: I don't know, man. Stuff happens. When one famous wizard dies other wizards usually show up to take everything they can find. Nessy wants to survive and take care of her cursed pals and ghosts. The bi-bopping around from character to character in the first half of the novel really dragged things out.
1. It looks like Martinez'z Constance Verity series has been optioned and will be filming. But, who knows? Names get listed to all sorts of media projects and things never happen.