The Circle Opens is a quartet of novels written by Tamora Pierce and set in a pseudo-medieval/renaissance era. It mainly revolves around four teenage mages, each specializing in a different kind of magic, as they find that they are forced to deal with mages whose powers are similarly unusual to their own. The series consists of the books Magic Steps (2000), Street Magic (2001), Cold Fire (2002), and Shatterglass (2003). The Circle Opens Quartet is the sequel quartet to The Circle Of Magic Quartet, and is followed by "Battle Magic" and The Will of the Empress. Source: Wikipedia (en)