Not a book: a library. Biblia is Greek for “the books”.
Christianity’s scripture comes in two parts. The Old Testament is the Jewish scripture, the Hebrew Bible, written mostly in Hebrew over many centuries before Christ; it opens with The Torah. The New Testament adds 27 books in Greek from the 1st century AD: four Gospels, the Acts, the letters (many by Paul) and Revelation.
How many books in total depends on who you ask: 66 for Protestants, 73 for Catholics, more for the Orthodox churches.
It was also the first big book printed in Europe with movable type, Gutenberg’s, around 1455. And it’s the most translated book ever: by 2025, more than 99% of the world’s population had at least part of it in a language they use. Phrases from it are everywhere, sometimes in disguise: Shibboleth comes from the Book of Judges.