The Blue Girl, Dingo, and Little (Grrl) Lost--and they are available in our teen sections, but his adult books are equally compelling and take place in the same universe.
His particular niche is called "urban fantasy," because instead of being set in some mythical kingdom or strange land that he "world-built" from scratch, the stories are set in an urban environment, i.e., in the city. This gives them more of a modern feel than what we typically think of as fantasy (Lord of the Rings, for instance), because it's as if we're in a contemporary, everyday place where magic is not the norm, but it still manages to creep in around the edges.
Picture yourself, for instance, walking down a busy street or through a city park. You catch a fleeting glimpse of a person that you could swear had horns growing out of his head, but then you decide that of course it must have been a hat. You see a couple of crows perched in a tree, and for an instant they look like a couple of raggedy goth girls dressed in black, but then the crows fly away and you mutter to yourself, "Got to get some coffee." The characteristic of urban fantasy is that it's happening all around you, but most people remain oblivious as they go about their day of commuting, working, playing, eating, and sleeping. The weirdness comes to a character's attention because something causes him or her to step outside of daily routine, and he is suddenly able to see more.
Charles de Lint is one of the masters of this genre. He has created a fictional city called Newford, which is loosely based on his home town of Ottawa (in Canada), although he maintains that Newford is an American city, and is much larger than Ottawa. It's hard to say just how many books he has set in and around Newford, but I counted more than 40 books on his website, and most are urban fantasy. He is one of the few writers whose short stories I enjoy; I don't usually care to read short stories (it's too truncated a format for me), but de Lint's all hang together around central themes that make them more like continuing narratives than individual stories.
On his website, he has a suggested order for reading the books set in Newford:
Dreams Underfoot (collection)
Memory and Dream (novel)
The Ivory and the Horn (collection)
Someplace to Be Flying (novel)
Moonlight and Vines (collection)
Forests of the Heart (novel)
The Onion Girl (novel)
Tapping the Dream Tree (collection)
Spirits in the Wires (novel)
Promises to Keep (short novel)
Muse and Reverie (collection)
Although I have enjoyed all those I have read, my favorites are Trader, and Memory and Dream.
Both of these books are wonderful on so many levels--the world-building, the characters, the narrative, the magical realism verging on fantasy. I hope this will inspire you to try one of them and see if you, too, would like to be an inhabitant of Newford for a while.