Amount of book: NaN
The purpose of this calculator is to calculate how many books you need to reach your required enchanted level.
For example, suppose you want to get Sharpness V (target) but you have a villager with Sharpness II (base).
In that case, the calculation will be 2target - base, or 25 - 2 = 8 books of Sharpness II to get a book of Sharpness V.
Although you can't go any higher in Survival mode, I still expanded the input in case you play modded Minecraft. It might go well beyond the normal cap of level 255.