You haven't really gone crazy until you've gone Cthulhu crazy.
In HP Lovecraft's Cthulhu Mythos stories, tomes of ancient and eldritch knowledge like the Necronomicon are highly sought after by those willing to trade their sanity for power. As the Mythos has continued to grow - sprouting more stories, a few table top role-playing games, and at least one first person shooter - cultists and sorcerers with heads full of unholy secrets gleaned from grimoires threatened the world on a fairly regular basis. In Issue 300 of The Escapist, Adam Gauntlett looks at the almost Faustian bargain that such books represent, and how the concept evolved over time.
Lovecraft used the Necronomicon as a means of conveying information. In his short story The Hound ... the book is doing double duty, allowing the author to give a description of the thing without going into excessive detail, and hinting at a long and awful backstory, without overwhelming the reader with that backstory.
Later, Lovecraft would use the Necronomicon less as a framing device for monsters and more as a hint of the antagonists' true nature. Merely owning the book is enough to show that the owner is up to something seriously dodgy, and wanting to read it, as Wilbur Whateley did in The Dunwich Horror, is proof of guilt; a literary equivalent of the smoking gun.
Call and Trail of Cthulhu are investigative games. The characters, often with no prior knowledge or interest in the occult, are thrust into a situation that they did not wish for and then must solve the mystery ... In this narrative, the grimoires ... have several roles. They're a source of general information and spells that boosts the character's knowledge base, allowing them to at least make an informed guess as to the opposition's strengths and weaknesses, as well as giving them a means by which they can retaliate. This gives the players a certain amount of control over their own destiny, while at the same time reinforcing the very real nature of the threat they face.
Lovecraft's tomes are the living embodiment of two old sayings: knowledge is power, and power corrupts. You can read about the dread Necronomicon and the rest of Lovecraft's arcane library in Gauntlett's article, "Pages of Power."