A snarkling follows up on the how long is too long post:
And is there such a thing as too short a word count? At what point to do the numbers by themselves start to make you apprehensive?
anything under 50,000 is going to make me look up how to spell "novella". Books get too small and people aren't willing to pay $23.00 for a hardcover.
Exceptions to this are graphic novels which are not measured solely by word count.