Boy is this a moving target now with the rise of the ebook revolution.
Let's take a peek at what the standard word count range is for Print Books - especially if you are trying to pursue a Literary Agent then a publisher.
However, its best to break it down by genre - in PRINT Books:
Overall for Adult books:
80,000 – 89,999 words
SCI-FI AND FANTASY
32,000 – 40,000 words
55,000 – 69,999 words
NOW with the rise of the ebook all of the above is different if you DON'T PLAN ON PRINTING the book.
With short story formats in ebooks rising many authors don't need to hit the higher word counts above for adult books in order to make the reader happy.
WHY THE STRINGENT cap on word count?
Well as authors we love to get lost in the story, but for a publisher to PRINT a book and EDIT a book the cost to benefit rises by page/word count. Therefore the Publisher has to pay more to print the books which means the PROFIT hurts with the larger word novels if the publishers wants to COMPETITIVELY PRICE the book for sale with other books in the genre.
As a SELF-PUBLISHER or SMALL PRESS does this matter?
Yep, it does, because you still want your print release prices to be competitive and the lost in prices as the page count rises isn't worth it for a small press just starting out. HOWEVER, if you only plan on releasing a book in ebook you have much more flexibility.