The Great Covenant Book of Jokes was a holy text written by the Prophet of Lies, but he died soon after (bummer). It was then that the Prophet of Truth finished the book for him. It was designed to keep up Covenant morale and spirit, but was soon discovered to consist of truly dreadful jokes, and has been deemed their downfall in the Human-Covenant War. It has been confirmed that this is the only book in the libraries of Covenant and has been attributed as the #1 cause of suicides on the Covenant side. How ironic.