on Just Publishing Advice:
There is no hard an fast rule. In some ways, it is a bit like asking how long is a piece of string.
In today’s publishing world, does word count matter anymore?
If you are pitching a new novel to a literary agent or publishing houses, yes it probably still does. You should always note your word count in your query letter.
But if you are self-publishing, you have much more latitude with your word and page count.
Is there a guide to how many words long a novel should be? No, but you can look at commonly accepted standards for popular book genres.