Enchanted books keep the "RepairCost" NBT tag after being unenchanted by a grindstone, causing the book to not stack with other normal books. The book still behaves like any other book, and doesn't seem to have any side effects
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This should probably be marked as duplicate, I had done some research before without finding it, but just found MC-148476
Posted something similar regarding a disenchanted iron Pickaxe still costing 32XP to repair post-disenchant