The book wasn't switched out. The new cases are pretty much tamper-proof. if it was opened, it would be very obvious. I'm thinking the grade is also legit and the book wasn't damaged inside the case. The corners, while somewhat unsightly, would be considered bindery tears by CGC and thus A-Okay on a 9.8 book. Is this worth a return to the seller? Well, if the book wasn't damaged in transit and there aren't any shenanigans with tampering then it seems like you got exactly what you paid for - a comic graded CGC 9.8. If CGC didn't grade this one strict enough, I'm not sure how that's on the seller.