To avoid bending, just place the manga beneath a pile of other books, which will probably result in them flattening immediately after some time. If you need to avoid the backbone breaking, just be cautious and feel the book – when you're feeling the book resisting more widening, just halt https://docs.google.com/document/d/1M-rCM_VHT6GkE1qBRxSsELDVWfXXqxv5YPs2lgf49jE/edit?tab=t.0