When I picked up Neil Gaiman's Coraline , the question wasn't whether or not I would like it; I knew I would. The question is whether I'd end up classing it as a significant work (like Sandman or American Gods) or a minor one (Stardust, Neverwhere). The small size of the book -- it's only 160 pages, with large line-spacing -- argued for the latter, but you never know.
After reading it, it's very definitely a minor book. It's well-crafted and written, with some truly great lines, but there's very little to it. Unlike Terry Pratchett's recent Discworld book and Pullman's trilogy, which were putatively aimed at children, but differed in no way from adult fare, Gaiman's book is a children's book through and through. The characters, the story, and even the writing style are all geared toward a younger crowd.
This isn't a bad thing, necessarily; as I said, it's a fine book. It does, however, mean that there's a sense of smallness and spareness to the book that prevents it from being truly great or memorable. There's just not enough story here to really support anything grand. Ultimately, Coraline reads more like the centerpiece of an anthology of short fiction than a standalone novel: I'd rave about "Coraline" if it were included in Smoke and Mirrors, but I can only say quietly nice things about Coraline.