This is a book that dates to early Canaanite times, roughly 1500 BC, It was written in the earliest known actual alphabet (as opposed to hieroglyphic or syllabary scripts). The only known copies that still survive are engraved onto thin copper sheets rather than written on papyrus.

While no one now knows the Canaanite language, it is closely related (maybe even ancestral) to both Hebrew and Aramaic. If a character knows either language he can attempt to decipher the book by rolling an Intelligence Check at Disadvantage. If he knows both languages he can decipher the book with a straight Intelligence Check, no disadvantage.

If deciphered, a zealot or scholar who reads the book will realize that it contains much of the source material for some of Kabbalistic tradition. Studying the book will reveal that it contains the formulae for making the magic items Shield of the Wall, Bag of Holding and Sword of the Warrior. Studying the book diligently and exclusively for a month will teach the reader the Cantrip “Whispermind” for free, in addition to his other cantrips.

The book is considered uncommon, not rare, because much of its information can be found in other books. It is not blasphemous.