This literally “little gray spellbook” contains a few rare spells and has a few empty pages when found. Per the rules, slightly modified1) it weighs just 2 pounds, is tiny2), has just 10 pages3), and can only be read by someone that can cast Identify. Please note that these spells are all from another era of D&D and a few fine points might have to be discussed to make use of them for the first time. They book referenced is from the DM's private collection.