Jews and Christians believe that the ultimate author of the Bible is God, via more or less direct inspiration given to human writers. Who and how many people were involved in the writing of the Bible is a matter of both historical and religious debate.
Traditionally, Jews ascribed the writing of the Torah, a piece of literature that constitutes the first five books of the Christian Old Testament, to Moses. Many historians disagree and believe that these books were written by multiple people over a long period of time. Historians distinguish the differing writers of these books mainly by their preferred word for God and the content of their passages. Other books, such as Isaiah, are also believed to have had multiple writers based upon analysis of differing literary styles within the same text.
The scholarship on the Gospels in the Christian New Testament is more straightforward, as they are generally thought to have been written by one individual each. Some devout Christians believe that there were 40 total writers of the Bible: 30 of the Old Testament and 10 of the New Testament. Historians are not as confident on the precise number of human writers and continue to debate Biblical authorship.