The Protestant canon has 66 books: 39 in the Old Testament and 27 in the New. Its Old Testament contains exactly the Hebrew material of the Tanakh, differently divided and differently ordered, and nothing else. The Reformers held that books not preserved in Hebrew lacked authority, and Luther grouped them separately as Apocrypha, useful but not doctrinal. Later English editions dropped them altogether, which is why most Protestant Bibles today print 66 books without comment.
The Catholic canon has 73. It adds Tobit, Judith, Wisdom, Sirach, Baruch and 1 and 2 Maccabees, plus Greek additions to Esther and Daniel, and calls them deuterocanonical rather than apocryphal. These books were in the Greek and Latin Bibles of the early church and in general Western use for over a millennium; the Council of Trent, in its decree of April 1546, made their status binding doctrine in response to the Reformers' rejection of them.
Eastern Orthodox Bibles go further, following the Septuagint: they include the Catholic deuterocanonicals and add 1 Esdras, 3 Maccabees, Psalm 151 and the Prayer of Manasseh, with 4 Maccabees usually printed in an appendix. Contents vary between the Greek, Slavonic and Georgian traditions, and no single Orthodox number can honestly be given.
The Ethiopian Orthodox Tewahedo canon is the widest. It is traditionally said to comprise 81 books and includes 1 Enoch and Jubilees, which no other church treats as scripture, together with Ethiopic works such as 1-3 Meqabyan, unrelated to the Maccabees of other canons. The figure of 81 is traditional and the lists that circulate do not consistently reach it, since sources differ on how books are counted and grouped.