execute as @s run data remove storage custom_item_model_data:item_model Model
execute as @s run data modify storage custom_item_model_data:item_model Model set from entity @s Inventory[{Slot:-106b}].components.minecraft:writable_book_content.pages[0].raw
execute as @s run function custom_item_model_data:set_model with storage custom_item_model_data:item_model {}

execute as @s run scoreboard players reset @s CustomModel
scoreboard players set @s CustomModel 0
scoreboard players enable @a CustomModel