Diana Wynne Jones, Mixed Magics.
I did a search the other day, and discovered the existence of two Chrestomanci books I'd not read before. I had my favourite children's librarian obtain this one for me.
Mixed Magics is a collection of four short stories: "Warlock at the Wheel," "Stealer of Souls," "Carol Oneir's Hundredth Dream," and "The Sage of Theare." All but one of the stories involve calling out the name and having that dapperly dressed Enchanter (well, when he isn't in a dressing gown, but even that'll be quite nice) show up and help out with the situation.
I don't think any of the stories are all that exciting: they're too much the writing of someone not content to leave stories off in places that invite readers to wonder. All the same, it's fun to spend time with Cat again, and in the worlds of the honourable Mr. Chant.