Sooner or later a party finds somebody else’s magic: a wizard’s spellbook in a ruined tower, a village wise woman’s book of charms, a codex a machine cult burned its own archive to hide. Handing the players the book, rather than a line on a loot list, makes them decide whether to open it.
The first page is the object: its title, whose it was, the school of magic, the language it is written in, its condition, what the binding and the pages look like, an inscription or a warning on the flyleaf, and a picture if you have one. The second page is the chapter of spells, each with its circle or rank, its cost or components and its effect, and a closing note on what study costs the reader. None of it is tied to one system, so the circle and the cost are whatever your game calls them.
Four books to choose from: a scholar’s spellbook with red rubrics and a gilded initial, a hedge witch’s charm book written by hand on odd scraps of paper, a forbidden codex from a far-future machine cult, and a folder of photocopies from a present-day investigation, with a sticky note and somebody’s biro on it. Both pages are A5 at 300 DPI and also print on an A4 sheet folded in half. The 1920s counterpart is the Mythos Tome, and a single spell for the table is a Reference Card.