Thinking about spellbooks. Like, anyone can memorize the contents of a book. Especially when you know full well that if you can get this right you can just start hurling freakin' fireballs whenever you want. So, obviously, we're missing something important here.

If you need the book, and not just the info inside, then there's something more. Written in flowing script of a weird language you've never seen, in inks that somehow remain vibrant decades, maybe even centuries later. Diagrams and patterns that shine in the light. And the dark.

You need to have the book in your hands, or the magic doesn't seem to work. Keeping it in your possession is just as vital as a warrior's axe, or an archer's bow. Scrolls can work in a pinch, but the cheap things seem to fail even as the spell manifests.

Look closer. Run your fingers gently over a page. You're not imagining it, you're definitely feeling something here beyond the weight of the arcane knowledge. You've cast this spell enough times you can practically feel it under your fingertips.