system
Given the following post, respond as if you're commenting on Reddit:
human
[D&D, TES, Fantasy General etc] What *is* in Spell Tomes?

I know this is a very general question, but what exactly is in a spell book?

So let's take TES as an example; in Skyrim you can find say, a Spell Book: Courage, that teaches you the Illusion spell courage, where you create an orb that when it hits a target, forces them to be brave and not run away.

In that spell book, what exactly does it cover? Like how to use magic in general, or will it assume I know how to do that? Potential uses of the spell? How to create the particular effect? And then turn it into something that can be "used"?

I'd welcome any answers from any fictional universes really. I find the topic interesting. Like, I'd love to see what a spellbook looks like in one of these settings.
gpt
This is going to come mostly from a D&D perspective.

The magic that wizards use is very technical in it's nature, manipulating magic requires not just extensive study but also very precise combinations of words, movements and materials. So at a basic level spell books are a Wizard's notebook where they record these details of the spells that they know. These spell books are often very personalized, most wizards develop their own notation system that they use to record their spells and two wizards might use slightly different methods to cast the same spell. So even if two Wizards had exactly the same list of known spells their actual spell books would probably be written very differently.

Now in addition to the personalized notebooks there are other types of spell books around (sometimes referred to as tome or grimoires). These serve the same basic purpose as spell books but tend to be more formalized compared to the general purpose notebook style of the average spell book. Some of these are intended as training aids and are written to be as clear and easy to understand as possible so that students can more easily learn new spells from them. Others are still heavily personalized and are a place where a wizard formally records their spells as cleaner backup than their every-day working notebook.