Ghostopolis by Doug TenNapel (2010)
Frank Gallows is a ghost hunter, a member of the Supernatural Immigration Task Force. It's Frank's job to sent ghosts of all sorts back to the other side, and in this book the other side is Ghostopolis. Time does not matter on the other side -- it does its own wonky thing. Thus it was possible for Joe, a Tuskeegee airman, to build/create Ghostopolis bit by bit in six days (or maybe a billion years, take your pick). Ghostopolis is just a way station for something bigger and brighter and (for the purposes of this graphic novel) unknowable.
Frank finds himself hunting a night mare -- the skeletal ghost of a horse. Just as he is sending the horse back to the other side, the night mare leaps through the wall of a house landing on top of Garth Hale, a young boy who is then accidently zapped to the ghost realm along with the night mare. The thing about Garth is that he would soon be going to the other side no matter what: he's dying of some unnamed disease. Frank's task force has to retrieve Garth so he can spend what little time he has left back in the earthly realm. Alas, Frank won't be going with the task force. He has been fired for incompetence.
Frank turns to his former girlfriend for help, the ghost Claire Voyant, whom he has conveniently failed to report to his superiors. Claire has a machine that has just enough power to take them to Ghostopolis and back. They head off to find Garth...
...Who faces danger in Ghostland. Luckily Garth falls in with another boy who tries to help him return. The other boy is Garth's own grandfather (I said time was wonky over there), and he and Garth, along with the Skinny, the skeletal night mare, head off for the capital of Ghostopolis. Adventures continue, culminating a epic battle of good versus evil.
Writer/artist Doug TenNapel, the creator of Earthworm Jim, has produced a thoroughly entertaining book with humor and insight. Ghostopolis reminds me strongly of Jeff Smith's Bone with it's simplicity of detail and strong characterization. Published for the YA market by Scholastic, Ghostopolis is an enjoyable experience for any age.