Books are things that people use to record and recall facts, information and ideas. They are usually made up of lots of rectangular pieces of paper, called pages, stuck together along one edge. Sometimes bookmakers put slightly larger, harder pieces of paper outside either end of the stack of paper to protect the pages. These are called 'covers'. Between these covers, on the pages are words.
There are many, many, many books in the world. Most of them have different sets of words inside them, but some of them are very hard to tell apart if you're not paying attention. A good way to tell books apart is by looking at the picture on the cover. This serves the purpose of letting you know if a book will be interesting to you, without you having to open it up and read it, in the same way that a can of soup is identifiable by the picture of a bowl of soup on the front of it.
The people who write the words in the books are called 'authors'. When they write from their imagination, rather than facts, it is called fiction. They almost always make things up about people that they have also made up. Sometimes they make up things about real people, but that can result in law suits.
Making the sets of words up is called writing. Basically anyone can do it, but the safest way to make sure that people give you money for your book is to not waste time on the words inside, but instead do make sure that your name is in big metallic letters above the title.
Once you have written enough books to make lots of money and have become a household name, stop doing it. That will get people excited and they will want to know when you will start again.