The Book of Ruth in the Bible Encyclopedia - ISBE

1. Order in the Canon: The place which the Book of Ruth occupies in the order of the books of the English Bible is not that of the Hebrew Canon. There it is one of the five meghilloth or Rolls, which were ordered to be read in the synagogue on 5 special occasions or festivals during the year. In printed editions of the Old Testament the megilloth are usually arranged in the order: Cant, Ruth, Lamentations, Ecclesiates, Esther. Ruth occupied the second position because the book was appointed to be read at the Feast of Weeks which was the second of the 5 special days. In Hebrew manuscripts, however, the order varies considerably. In Spanish manuscripts generally, and in one at least of the German school cited by Dr. Ginsburg (Introduction to the Hebrew Bible, London, 1897, 4), Ruth precedes Cant; and in the former Ecclesiastes is placed before Lamentations. The meghilloth constitute the second portion of the kethubhim or Haigographa, the third great division of the books of the Hebrew Scriptures. The Talmud, however, dissociates Ruth altogether from the remaining meghilloth, and places it first among the Hagiographa, before the Book of Psalms. By the Greek translators the book was removed from the position which it held in the Hebrew Canon, and because it described events contemporaneous with the Judges, was attached as a kind of appendix to the latter work. This sequence was adopted in the Vulgate, and so has passed into all modern Bibles...

Link: https://bible-history.com/isbe/R/RUTH,+THE+BOOK+OF/