Back at HarperCollins, our boilerplate contract used to state that an author would deliver a novel with a wordcount of between 120,00-180,000 words, which comes out to approx. 250-350 pages for a typical novel. But we always modified the word count, as any given author would vary greatly from book to book. And word count has almost nothing to do with page count. that is almost entirely dependant on the layout & design of the book. We used to specify on the production sheets that a novel was to be 300 (or whatever # we wanted) pages in length, and then the designer would layout the book to fit that, adjusting font, font size, margins, white space, headers/footers, chapter heads, etc to meet the page count we needed. There are all sorts of tricks you can use to adjust the page count of a book, and the reader hardly ever notices. Then you get into paper thickness and weight, and you can make a 250 page book thicker than a 400 page book...