Every good book has a theme, what is the theme of the Bible?

The theme of the bible is Jesus Christ. It is the story of mankind constantly rebelling against the God of rightness, and God has to send a savior so mankind can have spirit like they did in the beginning. The first prophecy of the savior is Genesis 3:15. The new testament has four gospels because there were four prophecies: a king, a servant, a man, and the son of God. Matthew is the story of a king with the genealogy in ascending order because a king traces ascent to the throne. Mark is the story of a servant with no genealogy. Luke is the story of a man with genealogy in descending order because a man traces descent from an ancestor. John has a very short genealogy: he is the son of God.

It is not reliable to let people tell you what the bible says. Many people will make up stuff because they don't know what it says, and many will make up stuff because they wish it would not say what it says. You just have to read it for yourself. Read a chapter of Proverbs every day. Proverbs has 31 chapters so you can keep your place by just looking at a calendar. There is no religion or nothing in Proverbs and you don't have to believe anything. Just read to find wisdom. When you are comfortable with that, then read the bible from Romans to 2 Thessalonians over and over until you start to remember what it says. That is the part that applies to Christians. Here is a book to help you to understand the bible. It's a free download and you can get a hard copy at any bible book store.
philologos.org/__eb-htetb/ "How To Enjoy The Bible"