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.
> 
> [Any sufficiently advanced magic is indistinguishable from technology.](https://tvtropes.org/pmwiki/pmwiki.php/Main/SufficientlyAnalyzedMagic)
> 
> 
> 

If you try to make sense of it, it stops being magic.

If that is not a satisfactory explanation for you, remember that on the disc, nothing is constant for too long. Even the stars tend to move and form new constellations, much to the chagrin of astrologers.

Last but not least, we are getting that information from secondhand sources and hearsay. Take the Rite of AshkEnte, for example. It only takes a simple incantation and two cc's of mouse blood, but if you ask the faculty for instructions they will include candles, cauldrons, a circle of eight and more paraphernalia. If you don't know better you may be fooled by wizards' love for power displays and drama.