It's kind of summary-proof, but I'll give it a go. It's the first in a long-running series about the Discworld. It's a disc-shaped world held up by four large elephants riding on the back of a giant, space-swimming turtle. The main plot is of a tourist named Twoflower from a far away land who has made his way to a major crime-infested city and has gotten a miserable wizard named Rincewind to be his guide. Twoflower is the owner of a frightening bit of self-propelling luggage that, well, I'll let you read it yourself if care to know more at this point.
I snagged it for my Kindle some time ago when it was on sale for cheap. Our book club is going to be doing another Discworld book later in the year, so I thought it would be good to finally read it so I have some knowledge of the world before we get to that (I think the eighth one? But I'm assured they don't need to be read in order).
This makes fun of everything. Gods, death, fate, heores, myths, dragon riders, tourists, etc. It even has a go at a Lovecraftian horror somewhere in there. It's a total hoot and I look forward to getting to a few more of these in the not-too-distant future!
Before I go, let me just fill you in on Pratchett's style and let him describe for you the actual color of magic:
A double rainbow coruscated into being. Close into the lip of the Rimfall were the seven lesser colours, sparkling and dancing in the spray of the dying seas.
But they we pale in comparison to the wider band that floated beyond them, not deigning to share the same spectrum.
It was the King of Colour, of which all the lesser colors are merely partial and wishy-washy reflections. It was octarine, the colour of magic. It was alive and glowing and vibrant and it was the undisputed pigment of the imagination, because wherever it appeared it was a sign that mere matter was a servant of the powers of the magical mind. It was enchantment itself.
But Rincewind always thought it looked a sort of greenish-purple.