I have been told by an assistant of a literary agent in New York City that debut authors should stay away from pitching a book that's over 70,000 words, and less than 55,000. Is this universal for the publishing industry? I have an unpublished debut novel entitled ISA and it's about a persecuted Christian living in Saudi Arabia. It's about 70,000 words. I am getting worried. I also have a speculative fantasy novel based in a Christian afterlife called, A FATHER'S JOURNEY TO PARADISE, and it's broken into two parts. It's 98,000 words. My shortest novel is a coming-of-age one which is 56k.
The longer a book is, the more it costs to print, but there's an upper limit to how much people want to pay for a book. So, all other things being equal, publishers prefer books that are not too far above the minimum viable length. Any and all rules can be bent and broken for an established, successful author, but first timers do best by falling in with standard expectations.
This is not a hard-and-fast rule by any means, but, especially if you heard it from a New York agency, it's worth paying attention to.
Luckily you are not in any sort of trouble. There's almost no 90k manuscript that couldn't be improved by editing it down to under 70k. You'll end up with a better final book if you start with one that is too long and edit it carefully --you definitely don't want to start out too short and have to resort to trying to pad it somehow. Personally, I'd love to have the problem of having too many words on the page, it gives you so much more to work with.