Over-Hyped & Under Appreciated Books

Some amazing books seem to slip between the cracks and no one ever mentions them.  While other books that are just okay are hyped up, made into movies, have merchandise sold for them, are on everyone's blogs, etc.  I'm not sure why this happens, but it makes me sad that some of these books are not talked about more.

What do you think?  Did I miss any good books that are under appreciated?  What about any hyped books I didn't mention?