The Discworld Series (Terry Pratchett, 1983-)

Discworld is a comic fantasy book series by the British author Terry Pratchett set on the Discworld, a flat world balanced on the backs of four elephants which are in turn standing on the back of a giant turtle, the Great A'Tuin. The books frequently parody or at least borrow ideas from J. R. R. Tolkien, Robert E. Howard, H. P. Lovecraft, and William Shakespeare, as well as myth, folklore and fairy tales, often using them for satirical parallels with current cultural, technological and scientific issues.

In The Colour of Magic Twoflower is a tourist, the first ever seen on the Discworld. Tourist, Rincewind decided, meant idiot. Somewhere on the frontier between thought and reality exists the Discworld, a parallel time and place which might sound and smell very much like our own, but which looks completely different. It plays by different rules. Certainly, it refuses to succumb to the quaint notion that universes are ruled by pure logic and the harmony of numbers. But, just because the Disc is different doesn't mean that some things don't stay the same. Its very existence is about to be threatened by a strange new blight: the arrival of the first tourist, upon whose survival rests the peace and prosperity of the land. But if the person charged with maintaining that survival in the face of robbers, mercenaries and, well, Death is a spectacularly inept wizard, a little logic might turn out to be a very good idea...

The series consists now of over thirty books:

The Colour of Magic
The Light Fantastic
Equal Rites
Mort
Sourcery
Wyrd Sisters
Pyramids
Guards! Guards!
Eric
Moving Pictures
Reaper Man
Witches Abroad
Small Gods
Lords and Ladies
Men at Arms
Soul Music
Interesting Times
Maskerade
Feet of Clay
Hogfather
Jingo
The Last Continent
Carpe Jugulum
The Fifth Elephant
The Truth
Thief of Time
The Last Hero
The Amazing Maurice and his Educated Rodents
Night Watch
The Wee Free Men
Monstrous Regiment
A Hat Full of Sky
Once More, With Footnotes
Going Postal
Wintersmith
Thud