Spelltomes and grimoires requiring UMD or specific class/alignment spawn with various UMD requirements, some as high as 35 UMD. However, if placed into a player bookshelf fixture and then removed, the UMD requirements can change: some are reduced to 30 UMD. This creates copies of the book that now circulate with lower UMD requirements.
(Honestly though, it kinda feels like a feature. 
)
