As I recall, the world more or less progresses chronologically as the series goes on. Characters introduced in earlier books get older, die off, and new ones take their place in later books so if you want to have the "complete" background for whatever book you are currently reading, you should probably start with the first book, A Spell for Chameleon, and proceed from there. That being said, you could probably pick up any book in the series and get most of what is available out of it. Any pertinent information from earlier books will be reintroduced / explained as needed to further the present story. I haven't read anything from the series for well over a decade so this may not be accurate for more recent books, but I did read the first ten or so back in the day.