According to The Encyclopaedia of Hell (1998) agrippas (named after Heinrich Cornelius Agrippa) are "huge volumes, usually more than five feed tall, with pages made of human skin. Each contains the names of all known demons and lists spells for conjuring up fiends. [...] The books themselves are considered living things and must be handled very carefully to avoid provoking an angry spirit" etc.

The Encyclopaedia of Hell is quite honestly a dreadful pulp-paper piece of pablum full of mistakes and inaccuracies written in a kind of breathless tabloidese... But... were very large spellbooks ever called agrippas? Is it possible Miriam van Scott (author) is misinformed... or just making it up?

It's not in the dictionary. Wiki's got nothing.