I HAVE HELD OFF POSTING SO FAR! MY FAVOURITE BOOKS IN THE SERIES ARE THE BOOKS WITH DEATH AND HIS FAMILY AS THE MAIN STARS.
I also love Pyramids, Moving pictures, Guard Guards, in Fact I like all of them!
Also for those who have read pratchett already give Jason Cosmo a look brilliant stuff
http://en.wikipedia.org/wiki/Jason_Cosmo
also Craig shaw Gardener's Malkady of magics
and of course
The 'Myth' and 'Phule' series by robert asprin