The First Book of Esdras is the first book of the Apocrypha.  Jews, Roman Catholics, and Protestants do not generally recognize 1 Esdras and 2 Esdras as being canonical. Eastern Orthodox generally consider 1 Esdras to be canonical, but not 2 Esdras.  It was originally included as part of teh Septuagint (Greek version of the Hebrew Bible).  Most of the book summarizes parts of Chronicles, Book of Ezra, and Nehemiah.  The only new material is the “Tale of the Three Guardsmen”, a Persian folk story.