Put your spellbook in your bag of holding when you're not using it, tie the bag shut, and lock it in a chest when you're not awake and carrying it with you. Also, put some
Explosive Runes on the spellbook.
Given how important a spellbook is to an adventuring wizard, I'd say you don't need any extra reason to be paranoid about it in character - paranoid protection of the spellbook is the default normal behavior.