Writing a book

So I have always wanted to write a book, and some one once told me that I should do it before I turn twenty five. I turn twenty five next month, so I need to get on the ball. I started writing this morning. I started by writing an introduction about me and what the book might be about, which is really still a mystery. I was very entrigued by Blue Like Jazz by Donald Miller which is more like a collection of essays than a cohesive book, so I think this might come across like that. But we will see I guess.