It's a series of trilogies mostly, but each trilogy is better if you know some additional context from the previous works.
Start with Magician Apprentice (Riftwar Saga) and go from there. They are 100% my favorite fantasy books. The second trilogy reminds me of what fuedal Japan could have been like if there (clan wars, honor-driven behavior) but also with an "we are outside the law" council of magicians that govern themselves as a group. Fun stuff.