Hey,

The method Enchantment.canEnchantItem return always false on a book itemstack. However the book can accept almost all (if not all ?) enchantements.

Reproduction:

if(Enchantment.ARROW_DAMAGE.canEnchantItem(new ItemStack(Material.BOOK))) {
getLogger().info("Can enchant a book.");
} else {
getLogger().info("Cannot enchant a book");
}

display: "Cannot enchant a book." This is reproductible with any enchantment.