Hi,
You have 2 options for this:
1. Editing the EnchantCore.json config file and enable this option:
"Name Hydration": {
"Enabled": true,
"Accept Token Names (ec:id:level)": true,
"Accept Display Names ([E] Sharpness III Book)": true,
"Require Skin Match": true,
then when you create the item in the shop put for the name "[E] Sharpness I Book" or "ec:sharpness:1".
2. The easy option: Use a command reward instead of an Item Reward.
For example use the command:
enchantcore.givebook $player.id sharpness 1 1