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The collection of texts today known as the Bible were not written at once. There's actually a lot of interesting history about how it came to be, but the short of it is that there were a multitude of maybe-canon Christian texts floating around during the early period of Christianity. These texts were written decades or even centuries apart, and often falsely attributed to authors who did not write them. There was also the Septuagint, a Greek text which was a translation of various Jewish scriptures, many of which now form the Old Testament.
The early Christian church decided which of these were deemed to be canon and which were non-canon. The canon texts were compiled together to form what is now the Bible. Everything else that was deemed not canon is called the Apocrypha. Many of these texts were also deemed heretical or blasphemous to read, publish, or teach by the various ecumenical councils.
Each Christian denomination has a slightly different version of the Bible depending on which decisions and ecumenical councils they accept.
The most interesting difference would be the Bible of the Church of Jesus Christ of Latter-Day Saints (also known as the Mormon Church), which has an additional text called the Book of Mormon. That was written in the 19th century by a guy named Joseph Smith, an American religious leader who founded Mormonism. According to Mormon theology, it contains the revalations he received from God about various other unknown saints who lived in America and other holy happenings which took place, making the US a second holy land of sorts. His group travelled to the western United States to find their own promised land and establish a Mormon theocracy (they were successful; it's now the US state of Utah).
There's no historical evidence that any of these texts were intended to be read as anything other than religious scripture, but keep in mind that in Biblical times, people seemed to have had a really difficult time differentiating texts written by people having fever dreams versus actual genuine accounts of observed events or legitimate attempts to write scripture. If you want a fun time, you can read some of the Apocrypha, which are often similar in style to the canonical gospels but are slightly... weirder. The line between religion and insanity was not so easily found back then. Regardless of their authors' original intent, the Apocrypha certainly can be read for entertainment in the 21st century.