It would help to know more about your business, but if you paid book royalties as an ordinary and necessary expense your business, you can deduct them. I would consider them to be more in line with Contract Labor (if you click on the more examples link, one of the examples is  Fees paid for creative resources. which may apply to your situation. This is a payment that may require you to issue a 1099-MISC to the recipient, so it would belong in this category.

Ultimately, it doesn't matter that much where you include it, as long as you don't double-deduct, and keep track of where you entered it. The result on your income taxes remains the same no matter where you put it.