I just got started with discworld as well! I started with the color of magic, which is the first one written. A few of my friends say the other ones that were published later are better, but I wanted to start at the beginning. I'm liking it, but not loving it. I'm towards the end of the book and I feel like the writing is getting a little disjointed. However I do plan to continue on with the series!
I know this is a common gripe on this site with some books but I was really annoyed to find the color of magic and a few others in the series priced at $9.99! For goodness sakes the series has been out I think since the 80's and the paper backs are 7.99! I've chosen to purchase the ones that are priced at 9.99 as used paper backs and will be buying the ebooks that are priced at 7.99.
eta- I found this fun chart for reading orders and entry points
http://www.lspace.org/books/reading-...r-guide-20.jpg