Why do Christians have different books in their Bible? Some Bibles have all 4 Maccabees books, for example, while others don't. Some Bibles have Esdras and Wisdom, and yet others don't.

Why is this? If there was an agreement on what books would be in the Bible in the early church, why are there so many differences between the books in various Bibles? Did some church leaders walk out and start there own churches with those books? Or is there some other reason?
Most of the books of the Bible were written by different people. An estimated 40 authors wrote the 70 or so books that various Christians accept as "the Bible". Most of these authors wrote independently from each other; if they were contemporaries, they typically did not confer with each other. If they were separated by time, the latter typically did not write with an apparent expectation that what he wrote would be considered scripture even though the former was during his time.

What you are referring to is the Bible Canon. A canon is


  a regulation or dogma decreed by a church council.
  Merriam Webster Dictionary


Basically, many Christians already followed many or even all of these books as scripture, then through councils called by early church leaders, a canon was set, decreeing them as scripture, indeed. These councils also set out to decree some theologies as Christian dogma and others as not Christian dogma. More rarely, some books were explicitly decreed not canon. These typically go by the names Apocrypha/Deuterocanonical books, Gnostic Gospels, or Pseudepigrapha. These books were accepted by fringe groups and rejected by the larger majority. This and among real issues (some teach dissonant doctrine) is why they were not included in the Biblical Canon. Most of them were just ignored or so fringe they were unheard of among the council members. 1

Today, there are three primary canons: The Catholic bible canon, the Protestant bible canon, and the Eastern/Greek Orthodox bible canon. In general, there was only the Catholic bible canon until Martin Luther started the Protestant Reformation in the 16th century. Martin Luther had many ideas that radically changed the face of Christianity, including views that led to the formation of the Protestant bible canon, which essentially removed 7 books from the Catholic bible canon and a few portions of some other books, but added nothing. Those books/portions present in the Catholic bible, but not in the Protestant bible are:


Tobit
Judith
Additions to Esther (Vulgate Esther 10:4–16:24)
Wisdom (also called the Wisdom of Solomon)
Sirach (also called Ecclesiasticus)
Baruch, including the Letter of Jeremiah (Additions to Jeremiah in the Septuagint)
Additions to Daniel:


Prayer of Azariah and Song of the Three Holy Children (Vulgate Daniel 3:24–90)
Susanna (Vulgate Daniel 13, Septuagint prologue)
Bel and the Dragon (Vulgate Daniel 14, Septuagint epilogue)

1 Maccabees
2 Maccabees
See "Deuterocanonical books - Wikipedia" for more information


The following table helps compare all the major canons. See the footnotes for a comprehensive list of all the books.


Source

There are a few other canons in some much smaller segments of the Christian population, but those are typically very small in their number of adherents. For example, the Church of Ethiopia has a few more books in their canon than the Catholic canon. 2

Summary

The books accepted by any Christian group is called a canon. There are three major canons, one for the Catholics, one for the Eastern Orthodox, and one for the Protestants. The canon was decreed as "scripture" by early church councils, mostly based on the widespread use of these books. Over the centuries, there has been plenty of debate on the actual authenticity of these books, from both historical and theological perspectives. To many theologians and historians, the authenticity of any given book is a matter of independent study of those individual books, and opinions tend to vary widely among theologians, but tend to fall one way or the other among historians.

Sources and further information


Biblical Canon - Wikipedia
Development of the Christian biblical canon - Wikipedia
Books of the Bible - Wikipedia

Other Questions on Christianity Stack Exchange
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How many &#39;Books&#39; never made it to the Bible (Old and New Testament)?
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Footnotes:


Disclaimer: This is a gross simplification of a long and complicated topic rife with historical debate that goes back to the second century and continues today. For example, this brief synopsis implies that Martin Luther is responsible for all of it, but that is far from the case. The differences between the Eastern Orthodox and the Roman Catholic churches manifested a thousand years before Luther and came to a head in the 11th century with the Great Schism. Further complicating the issue, what Christians call the Old Testament was part of the Hebrew/Jewish Bible canon which has its own long history of development that for the most part, Christianity just inherited. If you want to have a solid grasp on what actually happened, you will need to read no fewer than 200 pages on the subject.
There are, of course, some modern churches that claim the Christian title that have wildly different canons. The LDS church, for example, accepts the Protestant Canon, in addition to the many books found in the Book of Mormon, Doctrines and Covenants, and the Pearl of Great Price. There are no other Christians that accept these books as scripture.
Comprehensive list of all the books of "the bible" (Source):


  Hebrew Bible
  
  All extant manuscripts of the following texts:
  
  Torah (Books of Moses)
  
  
  Genesis
  Exodus
  Leviticus
  Numbers
  Deuteronomy
  
  
  The Samaritan Pentateuch is also included.
  
  Nevi'im (Prophets)
  
  
  Joshua
  Judges
  Kingdoms (I - IV)
  
  
  Samuel (I &amp; II)
  Kings (I &amp; II)
  
  Isaiah
  Jeremiah
  Ezekiel
  Twelve Prophets
  
  
  Hosea
  Joel
  Amos
  Obadiah
  Jonah
  Micah
  Nahum
  Habakkuk
  Zephaniah
  Haggai
  Zechariah
  Malachi
  
  
  
  Kethuvim (Writings)
  
  
  Psalms (including manuscripts containing 151 psalms)
  Proverbs
  Job
  The Song of Songs
  Ruth
  Lamentations
  Ecclesiastes
  Esther (including manuscripts containing The Additions)
  Daniel (including manuscripts containing Susanna, Bel and the Serpent/Dragon, and/or the Hymn of the Three Youths)
  Ezra-Nehemiah / Esdras (I &amp; II)
  Chronicles / Paraleipomenon (I &amp; II, including manuscripts containing the Prayer of Manasseh)
  
  
  Care should be taken to clearly refer to relevant sections of the
  Hebrew Bible as chapter and verse sections as well as the order of
  content is not consistent between many translations, manuscripts, and
  critical texts.
  
  
  
  Apocrypha
  
  All extant manuscripts of the following texts:
  
  Note that the use of the term Apocrypha as a proper title is
  defined on this site as referring specifically (and exclusively) to
  the following listed texts (and the word should always be capitalized
  when used in this manner on this site). It is known that other works
  such as the Gnostic gospels are commonly referred to as
  "apocryphal" texts, but as per our site standards only the
  below-listed texts constitute the Apocrypha.
  
  Texts and Additions to Esther and Daniel that are included in Roman Catholic, Greek, and Slavonic Bibles
  
  
  Tobit
  Judith
  Additions to the book of Esther in Greek manuscripts
  Wisdom of Solomon
  Ecclesiasticus (Wisdom of Jesus, Son of Sirach)
  Baruch
  The Letter/Epistle of Jeremiah (6th chapter of Baruch)
  Additions to the book of Daniel in Greek manuscripts
  
  
  The Prayer of Azariah and the Song of the Three Jews
  Susanna
  Bel and the Serpent/Dragon
  
  Maccabees (I &amp; II)
  
  
  Texts in the Greek and Slavonic Bibles but not in Roman Catholic Bibles
  
  
  1 Esdras (in Greek; 2 Esdras in Slavonic; 3 Esdras in Appendix to Vulgate)
  Prayer of Manasseh (in Appendix to Vulgate; included in some manuscripts of 2 Chronicles / Paraleipomenon)
  Psalm 151 (included in Greek manuscripts of Psalms)
  3 Maccabees
  
  
  Text in the Slavonic Bible and the Latin Vulgate Appendix
  
  
  2 Esdras (3 Esdras in Slavonic; 4 Esdras in Vulgate Appendix)
  
  
  Text in an Appendix to the Greek Bible
  
  
  4 Maccabees
  
  
  Care should be taken to clearly refer to relevant sections of the
  Apocrypha as text/book titles, chapter and verse sections as well as
  the order of content is not consistent between many translations,
  manuscripts, and critical texts.
  
  
  
  New Testament
  
  All extant manuscripts of the following texts:
  
  Homologoumena
  
  
  Gospels
  
  
  Matthew
  Mark
  Luke
  John
  
  Acts of the Apostles
  Epistles/Letters
  
  
  Romans
  Corinthians (I &amp; II, although historically they are believed to be the II &amp; III letters sent to Corinth, the first of which is extinct)
  Galatians
  Ephesians
  Philippians
  Colossians
  Thessalonians (I &amp; II)
  Timothy (I &amp; II)
  Titus
  Philemon
  I Peter
  I John (not to be confused with the Gospel of John)
  
  
  
  Antilegomena
  
  
  James
  Jude / Judah
  Hebrews
  II Peter
  John (II &amp; III, not to be confused with the Gospel of John)
  Apocalypse of John / Revelation
  
  
  These are the primary texts which constitute 'the Bible.'