A short novel; a novella.

A novelette (or novelet) is a piece of short prose fiction. The distinction between a novelette and other literary forms, like a novella, is usually based upon word count. The Science Fiction and Fantasy Writers of America Nebula awards for science fiction define the novelette as having a word count between 7,500 and 17,500, or 45-85 pages, in length.http://www.sfwa.org/awards/faq.htm Science Fiction and Fantasy Writers of America Awards FAQ.