Despite the name of this post, I am not going to call my new campaign Tomes of Magic. For one, it's far too on-the-nose, and it's just unimaginative.
However, magical works of writing will play an outsized role in the campaign, with the primary method of discovering new spells consisting of stumbling upon them in ancient lore or finding them scrawled on prehistoric tablets and scrolls. In fact, the PCs will be questing for the correct magical knowledge to take down whatever big nasty they may be facing as they progress through their careers (if they don't DIE of course).
In the spirit of this new campaign idea, I offer you a new magical tome, described below.
CROWN AND INFERNO
Author: Unknown
Crown and Inferno is large at 18 inches tall and 12 inches across the front cover, and is bound in red dyed leather with luxuriously smooth vellum pages. The tome seems ageless, remaining like new even over years of use and storage, with no fading inks or colors, and no wear to the binding.
Within the book, should a character peruse its contents, the hierarchies of Hell are explained in great detail, and the text abounds with purported True Names of demons, along with instructions for summoning their kind to the Material Plane. If the characters research the book before they attempt to read it, they may find out (an Intelligence check with a positive or negative modifier, depending on the accuracy of the research materials) that it may help to be warded against evil when reading. Just the first few paragraphs of the book are enough to potentially leave a character open to demonic possession. The GM is free to use the rules he likes for possession attempts, since many of these rules exist in different games, and many will work with old style rules.
Should the character(s) reading the text avoid any possession attempts that may befall them, they will be able to identify 1d4 different spells of any spell level, providing these spells can help in attempting to summon demons or extraplanar entities. The GM should choose the spells from the game rules he likes best, as long as they contain spells for demon-summoning. These spells may be transferred to a character's spell book in the usual time frame, and the spells may not be used from the book as a spell scroll would be used.
Only one attempt at spell discovery per character is allowed, and each will have to defend against demon possession. After the spells are discovered, the book remains in their possession, but is useful only as a reference for future research. It does not radiate magic, since it merely contains instructions for magical rites.