Don’t know it this is the right place but I’ll ask anyway. I have a maximum ride paperback book I lent to my grandma to read. When I got it back the spine was curved inward and more concave than before. How can I fix it?

I have it pressed in a tightly packed shelf to try to use pressure to straighten it but I don’t know how it would work. Or if there could be other ways to straighten it back to normal. It’s kind of annoying knowing it was straight and new looking before and is now is suddenly looking like I’ve had it for years. 🙁

by Whirlwinds228