It'a a picture book, fantastically illustrated by Dave McKean, about a little girl who hears wolves in the walls. Her family tries to convince her that it's something other than wolves -- mice, maybe, or bats -- but her family tells her that if the wolves come out of the walls, it's all over. So, of course, what happens but the wolves do come out of the walls, and hilarity ensues. It's delightfully creepy -- what do you expect, really, out of a kid's book by Neil Gaiman -- but I guarantee I would have loved this book as a kid. As a bonus, it features a pink pig puppet throughout the book, as well.
Wonderful book, my 7 yr old daughter and I read this together and we both just loved it!