The danger awaiting a book is lesser than the danger awaiting a saved recovery seed online, right? Books can get burnt or torn apart if carelessly handled and the worst that can happen is losing access to your coins, it's still better than someone stealing your coins.
After writing your recovery seed on a paper, you should have many backups of that seed phrase and in more than one location, the chances that all of them will get burnt, torn apart or destroyed in different places at the same time is minute. After writing your seed phrase down, you can as well laminate the paper to make things safer. Storing it online is one of the worst things anybody can do.