A grimoire—a manual of magic—is a spectacular undertaking and we applaud you for considering making one! As you write it, the grimoire acquires its own spirit called an Egregore, comprised of your intentions and energies, and the energies of those spirits/elementals/faeries/etc you are working with to create it.
Protecting it is a matter of preference and circumstance. If you find yourself in a situation where the book might be handled or destroyed without your permission, locking it in a drawer or box is a good option. If you want to be the only person who reads it, write it in a cypher of your own creation (just remember to keep the key for it in a safe place).