Instead of a string of sequels, the entire series was conceived as a single epic tale divided into individual episodes. All were written before the first was released so that plot elements are intertwined, yet each is self-contained with it’s own conflict and resolution.
The Riyria Chronicles is a prequel series to The Riyria Revelations which explores: the origin of the partnership between Royce and Hadrian, how Riyria was formed, and the adventures the two went on during the twelve years prior to the events in The Riyria Revelations.
While you can read the books in either publication order (starting with Theft of Swords) or chronologically (starting with The Crown Tower) the author suggest publication order as you are introduced to the characters and world as originally intended. In addition, there are some subtle winks and nods for veterans of Revelations when reading Chronicles. These aren’t major plot points just little extras for “those in the know.”