Number of writings
The Old Testament, as originally canonized by Ezra the prophet, was composed of 22 books (which is the same number of letters in the Hebrew alphabet). They were divided into three major sets which were the Law, the Prophets and the Writings (or Psalms, see Luke 24:44). It was not until much later that this inspired division was removed.
The New Testament, as canonized by the Apostle John, contained 27 books. Jerome's late fourth century A.D. Latin Vulgate version, however, which became the standard for the Catholic Church, contained a total number of 41. This added set are known collectively as the Apocrypha, a set of writing found in various translations such as the NAB and RSV.
Who wrote the most?
The Apostle Paul, by far, is the most prolific Biblical writer. He wrote fourteen books while Moses and the Apostle John penned five of them. The fourth most active contributor to God's word is the prophet Isaiah (he penned 1 and 2 Samuel, 1Kings, and half of 2Kings).
The books of the New Testament were written by only eight men. Determining how many contributed to the writing of the Old Testament, however, is a much harder task. At least twenty-seven individuals are known to have penned this section of God's word. An additional unspecified number of Davidic priests recorded Psalms 73 to 88 and 90 to 106. It is also unclear who wrote the book of Proverbs chapters 25 through 31. At least three, maybe more, writers contributed to this section of Proverbs.
The Most Referenced
The most referenced writings in the New Testament are those by Isaiah (referred to 419 times) followed by the Psalms (414 times) then Genesis (260 times). Revelation contains content from at least thirty-two distinct Old Testament writings, while Luke contains thirty-one and the Gospel of John has twenty-six.
Longest and shortest
The longest writing (based on the KJV Bible) is the book of Psalms. It has 150 chapters, 2,461 verses and 43,743 words. The longest New Testament writing, however, depends on what is being compared. In terms of chapters, both Matthew and Acts are the biggest with 28 chapters compared to Luke's 24. In terms of verses, Luke has more (1,151) than Matthew (1,071) or Acts (1,007). The Gospel of Luke also has more words (25,944) than either second place Acts (24,245) or third place Matthew (23,684).
The shortest of the Old Testament books is Obadiah. It contains one chapter that has only twenty-one verses with 669 words. The shortest New Testament writing depends on what measurement is utilized. Both 2John and 3John have one chapter. The book of 2John, while it contains less verses than 3John (13 versus 14), contains more words (298 versus 294).
Mentioned but not included
The Old Testament references the existence of several writings that are not included as part of the Holy Scriptures. These books include the wars of the Lord (Numbers 21:14) and those named after Jasher (2Samuel 1:18), Shemaiah the Prophet (2Chronicles 12:15) and Jehu the Son of Hanani (2Chronicles 20:34).
The acts of King David were written in the writings of Samuel the seer, Nathan the Prophet and Gad the seer (1Chronicles 29:29). The acts of King Solomon are stated to be in writings named after him (1Kings 11:41) and Nathan the Prophet (2Chronicles 9:29). They have also been recorded in the prophecy of Ahijah the Shilonite and the visions of Iddo the seer (2Chronicles 9:29).
The acts of evil King Manasseh of Judah, the longest reigning monarch over any of God's people, were written "among the sayings of the seers" (2Chronicles 33:13, KJV). Books of the chronicles of the kings of Judah (1Kings 15:23), Israel (verse 31), and both dynasties together (1Chronicles 9:1) are also recorded as existing at one time.