It's probably a legit 9.8 even with the spine ticks. Are there nicer 9.8s out there? Probably, But by the letter of the law those are not egregious enough to say it can't possibly be a 9.8.
What would I do in this situation? I wouldn't return it because the problem isn't on the seller. I assume there were pics of the book in the listing for you to examine and you chose to buy that particular book. If it bothers you, try to sell it to recoup your money and find another one. I've done this plenty of times. No guarantee you'll get all the money back you put into it, but chalk it up to the cost of doing business.