Question: In *The Colour of Magic*, we learn that:

> 
> "Can't tell you. Don't really want to talk about it. But frankly," he
>  sighed , "no spells are much good. It takes three months to commit
>  even a simple one to memory, and then once you’ve used it, pow it's
>  gone. that's what's so stupid about the whole magic thing, You know.
>  You spend twenty years learning the spell that makes nude virgins
>  appear in your bedroom, and then you're so poisoned by quicksilver
>  fumes and half-blind from reading old grimoires that you can't
>  remember what happens next."
> 
> 
> 

So clearly: a spell is something you need to create, and you can use but once. And it's something utterly useless as a consequence.

In *Equal Rites*, Esk is able to do MANY spells without creating any of them. And afterwards, it seems that *The Colour of Magic* description of how magic works never holds...

Does Rincewind lie? Is there an explanation I missed out?

Answer: 
Pratchett himself always claimed that all consistencies in his work were accidental so there almost certainly is an inconsistency. That's the first point.

Secondly Rincewind is a special case, he has a very nasty spell in his head that chases other spells away so what he says is probably his exact experience of trying to learn other magicks.

Thirdly Esk is a special case as well, she's a female wizard and many of the usual rules of magic do not seem to apply to her. Simon's even worse.

There also seems to be major difference between Magic and Spells in the Discworld setting. Spells as formalised rituals are used far less than Magic; raw power applied to problems using a rough and ready, brute strength and massive ignorance approach.
A strong thread throughout the Discworld books is the idea that *what people believe* causes *what actually is real on the Discworld* (and especially that our fiction drives the Disc's reality), and its close relative idea that *[narrative causality](https://wiki.lspace.org/mediawiki/Narrative_Causality) is a real force* and that *events on the Discworld actually do conspire to make stories true*. Discworld is like a mirror that takes themes and tropes from our fiction and shows them, distorted and changed around, in a new way.

Given these basic facts, which are pretty fundamental to the nature of reality on the Discworld, and the fact that *there are a lot stories that have different kinds of magic that work in different ways*, it seems pretty unremarkable that there are multiple different ways for magic to work on Discworld. It wouldn't be able to mirror our fiction effectively if it didn't have room for all of those ideas.