You need to modify the textures.
Just go in:
C:\steam\steamapps\common\SourceFilmmaker\game\workshop\materials\models\unconid\book\
and modify the book_u.vtf

Here's a guide if you're interested in knowing what section of book_u.vtf corresponds to what part of the model:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1761886674

引用自 sn0wsh00：

Here's a guide if you're interested in knowing what section of book_u.vtf corresponds to what part of the model:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1761886674

Nice, But it would be awesome to have some kind of landmark lines for the spine edges :p

引用自 Closed：

You need to modify the textures.
Just go in:
C:\steam\steamapps\common\SourceFilmmaker\game\workshop\materials\models\unconid\book\
and modify the book_u.vtf

Modify how?
Through the Blender?