Read the Bible through and through and it's obvious one book is missing. It's one that connects all the books together.
It's no book that any cannonical council forgot to include centuries ago. Yes it's one that God also inspires. It is one that can at times be read by others. It's not one we can read accurately for ourselves, though.
The missing book of the Bible is one that God writes in our minds and in our loving and lovable selves throughout our lives so others will experience for themselves what God is really like.