I've just started the Discworld books (currently on Sourcery) and completely acknowledge that I am arriving to the series late in the day. Now in the past I've always thought of the series as a little bit too daunting to start. There are a lot of books and when I've been into the book shops they always take up multiple rows. That being said I took the plunge ... And loved them !
I was warned by friends not to judge the first couple of books as indicative of the entire series and found this little bit of advice helpful. It did take the books a while to find a rhythm and for me I felt that was masterfully achieved in Mort. This is my favourite of the series so far!
The books are all set in a world that is a flat disc, the disc sits upon the backs of four elephants which in turn sit upon the back of a massive space faring sea turtle. On the disc magic is in abundance, death walks amount people and witches and wizards duel! The concepts in the book are familiar but fantastic at the same time and the writing style is clever and quick witted.
If you haven't read them I would encourage you to do so! If you like fantasy books I don't think you'll be disappointed but you may need to read a couple of books to get a true flavour